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	$172.52	8.586%	$187.3326	$187.33	$187.35	$187.30
Purchase #2	$142.38	9.484%	$155.8833	$155.88	$155.90	$155.90
Purchase #3	$123.31	5.603%	$130.2191	$130.22	$130.20	$130.20
Purchase #4	$186.58	9.817%	$204.8966	$204.90	$204.90	$204.90
Purchase #5	$61.83	6.345%	$65.7531	$65.75	$65.75	$65.80
Purchase #6	$206.81	5.838%	$218.8836	$218.88	$218.90	$218.90
Purchase #7	$88.27	11.500%	$98.4211	$98.42	$98.40	$98.40
7 purchase totals =	$981.70		$1,061.3894	$1,061.38	$1,061.40	$1,061.40