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	$160.86	12.675%	$181.249	$181.25	$181.25	$181.20
Purchase #2	$26.70	12.825%	$30.1243	$30.12	$30.10	$30.10
Purchase #3	$127.41	13.379%	$144.4562	$144.46	$144.45	$144.50
Purchase #4	$64.53	10.494%	$71.3018	$71.30	$71.30	$71.30
Purchase #5	$168.34	13.619%	$191.2662	$191.27	$191.25	$191.30
Purchase #6	$244.57	12.241%	$274.5078	$274.51	$274.50	$274.50
Purchase #7	$223.80	11.690%	$249.9622	$249.96	$249.95	$250.00
7 purchase totals =	$1,016.21		$1,142.8675	$1,142.87	$1,142.80	$1,142.90