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	$153.43	3.190%	$158.3244	$158.32	$158.30	$158.30
Purchase #2	$83.76	10.419%	$92.487	$92.49	$92.50	$92.50
Purchase #3	$58.45	5.541%	$61.6887	$61.69	$61.70	$61.70
Purchase #4	$197.46	10.842%	$218.8686	$218.87	$218.85	$218.90
Purchase #5	$67.44	6.328%	$71.7076	$71.71	$71.70	$71.70
Purchase #6	$134.61	13.447%	$152.711	$152.71	$152.70	$152.70
Purchase #7	$235.57	12.710%	$265.5109	$265.51	$265.50	$265.50
7 purchase totals =	$930.72		$1,021.2982	$1,021.30	$1,021.25	$1,021.30