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	$144.57	7.839%	$155.9028	$155.90	$155.90	$155.90
Purchase #2	$86.33	4.453%	$90.1743	$90.17	$90.15	$90.20
Purchase #3	$38.38	8.359%	$41.5882	$41.59	$41.60	$41.60
Purchase #4	$239.64	6.276%	$254.6798	$254.68	$254.70	$254.70
Purchase #5	$116.34	9.862%	$127.8135	$127.81	$127.80	$127.80
Purchase #6	$180.80	8.483%	$196.1373	$196.14	$196.15	$196.10
Purchase #7	$227.89	8.432%	$247.1057	$247.11	$247.10	$247.10
7 purchase totals =	$1,033.95		$1,113.4016	$1,113.40	$1,113.40	$1,113.40