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	$143.60	6.502%	$152.9369	$152.94	$152.95	$152.90
Purchase #2	$191.28	6.821%	$204.3272	$204.33	$204.35	$204.30
Purchase #3	$179.53	8.157%	$194.1743	$194.17	$194.15	$194.20
Purchase #4	$52.33	4.107%	$54.4792	$54.48	$54.50	$54.50
Purchase #5	$176.68	11.322%	$196.6837	$196.68	$196.70	$196.70
Purchase #6	$61.83	13.446%	$70.1437	$70.14	$70.15	$70.10
Purchase #7	$122.58	13.487%	$139.1124	$139.11	$139.10	$139.10
7 purchase totals =	$927.83		$1,011.8574	$1,011.85	$1,011.90	$1,011.80