Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$213.72	4.773%	$223.9209	$223.92	$223.90	$223.90
Purchase #2	$193.50	10.424%	$213.6704	$213.67	$213.65	$213.70
Purchase #3	$144.78	8.191%	$156.6389	$156.64	$156.65	$156.60
Purchase #4	$182.78	7.572%	$196.6201	$196.62	$196.60	$196.60
Purchase #5	$250.72	6.695%	$267.5057	$267.51	$267.50	$267.50
Purchase #6	$124.33	12.502%	$139.8737	$139.87	$139.85	$139.90
Purchase #7	$185.75	13.231%	$210.3266	$210.33	$210.35	$210.30
7 purchase totals =	$1,295.58		$1,408.5563	$1,408.56	$1,408.50	$1,408.50