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	$45.37	13.401%	$51.45	$51.45	$51.45	$51.50
Purchase #2	$193.65	8.809%	$210.7086	$210.71	$210.70	$210.70
Purchase #3	$155.36	6.627%	$165.6557	$165.66	$165.65	$165.70
Purchase #4	$244.72	4.430%	$255.5611	$255.56	$255.55	$255.60
Purchase #5	$108.90	13.536%	$123.6407	$123.64	$123.65	$123.60
Purchase #6	$141.68	9.448%	$155.0659	$155.07	$155.05	$155.10
Purchase #7	$156.45	7.300%	$167.8709	$167.87	$167.85	$167.90
7 purchase totals =	$1,046.13		$1,129.9529	$1,129.96	$1,129.90	$1,130.10