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	$100.81	5.834%	$106.6913	$106.69	$106.70	$106.70
Purchase #2	$170.67	6.404%	$181.5997	$181.60	$181.60	$181.60
Purchase #3	$188.90	11.421%	$210.4743	$210.47	$210.45	$210.50
Purchase #4	$185.81	5.729%	$196.4551	$196.46	$196.45	$196.50
Purchase #5	$197.95	12.721%	$223.1312	$223.13	$223.15	$223.10
Purchase #6	$47.47	10.230%	$52.3262	$52.33	$52.35	$52.30
Purchase #7	$200.76	13.531%	$227.9248	$227.92	$227.90	$227.90
7 purchase totals =	$1,092.37		$1,198.6026	$1,198.60	$1,198.60	$1,198.60