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	$186.42	3.490%	$192.9261	$192.93	$192.95	$192.90
Purchase #2	$172.46	6.773%	$184.1407	$184.14	$184.15	$184.10
Purchase #3	$115.82	10.765%	$128.288	$128.29	$128.30	$128.30
Purchase #4	$227.61	7.849%	$245.4751	$245.48	$245.50	$245.50
Purchase #5	$53.97	6.140%	$57.2838	$57.28	$57.30	$57.30
Purchase #6	$57.96	4.202%	$60.3955	$60.40	$60.40	$60.40
Purchase #7	$141.84	6.689%	$151.3277	$151.33	$151.35	$151.30
7 purchase totals =	$956.08		$1,019.8369	$1,019.85	$1,019.95	$1,019.80