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	$172.69	8.774%	$187.8418	$187.84	$187.85	$187.80
Purchase #2	$236.77	7.488%	$254.4993	$254.50	$254.50	$254.50
Purchase #3	$32.96	5.408%	$34.7425	$34.74	$34.75	$34.70
Purchase #4	$212.58	12.123%	$238.3511	$238.35	$238.35	$238.40
Purchase #5	$153.73	13.341%	$174.2391	$174.24	$174.25	$174.20
Purchase #6	$223.28	13.710%	$253.8917	$253.89	$253.90	$253.90
Purchase #7	$42.81	6.669%	$45.665	$45.67	$45.65	$45.70
7 purchase totals =	$1,074.82		$1,189.2305	$1,189.23	$1,189.25	$1,189.20