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	$172.89	10.241%	$190.5957	$190.60	$190.60	$190.60
Purchase #2	$16.41	11.625%	$18.3177	$18.32	$18.30	$18.30
Purchase #3	$218.57	12.339%	$245.5394	$245.54	$245.55	$245.50
Purchase #4	$106.71	3.560%	$110.5089	$110.51	$110.50	$110.50
Purchase #5	$138.28	8.404%	$149.9011	$149.90	$149.90	$149.90
Purchase #6	$100.75	10.535%	$111.364	$111.36	$111.35	$111.40
Purchase #7	$193.51	4.546%	$202.307	$202.31	$202.30	$202.30
7 purchase totals =	$947.12		$1,028.5338	$1,028.54	$1,028.50	$1,028.50