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	$56.90	7.416%	$61.1197	$61.12	$61.10	$61.10
Purchase #2	$71.39	9.353%	$78.0671	$78.07	$78.05	$78.10
Purchase #3	$100.47	9.407%	$109.9212	$109.92	$109.90	$109.90
Purchase #4	$108.46	3.169%	$111.8971	$111.90	$111.90	$111.90
Purchase #5	$26.51	6.220%	$28.1589	$28.16	$28.15	$28.20
Purchase #6	$46.86	10.686%	$51.8675	$51.87	$51.85	$51.90
Purchase #7	$218.33	8.128%	$236.0759	$236.08	$236.10	$236.10
7 purchase totals =	$628.92		$677.1074	$677.12	$677.05	$677.20