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	$53.37	11.605%	$59.5636	$59.56	$59.55	$59.60
Purchase #2	$76.39	11.515%	$85.1863	$85.19	$85.20	$85.20
Purchase #3	$134.57	13.367%	$152.558	$152.56	$152.55	$152.60
Purchase #4	$56.62	6.251%	$60.1593	$60.16	$60.15	$60.20
Purchase #5	$105.51	7.556%	$113.4823	$113.48	$113.50	$113.50
Purchase #6	$111.28	3.274%	$114.9233	$114.92	$114.90	$114.90
Purchase #7	$219.45	4.557%	$229.4503	$229.45	$229.45	$229.50
7 purchase totals =	$757.19		$815.3231	$815.32	$815.30	$815.50