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	$203.95	9.407%	$223.1356	$223.14	$223.15	$223.10
Purchase #2	$29.77	13.600%	$33.8187	$33.82	$33.80	$33.80
Purchase #3	$164.41	12.804%	$185.4611	$185.46	$185.45	$185.50
Purchase #4	$239.98	5.765%	$253.8148	$253.81	$253.80	$253.80
Purchase #5	$18.31	8.482%	$19.8631	$19.86	$19.85	$19.90
Purchase #6	$139.86	11.766%	$156.3159	$156.32	$156.30	$156.30
Purchase #7	$245.45	10.624%	$271.5266	$271.53	$271.55	$271.50
7 purchase totals =	$1,041.73		$1,143.9358	$1,143.94	$1,143.90	$1,143.90