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	$165.41	12.229%	$185.638	$185.64	$185.65	$185.60
Purchase #2	$201.65	7.739%	$217.2557	$217.26	$217.25	$217.30
Purchase #3	$159.43	7.738%	$171.7667	$171.77	$171.75	$171.80
Purchase #4	$155.77	12.462%	$175.1821	$175.18	$175.20	$175.20
Purchase #5	$67.72	4.501%	$70.7681	$70.77	$70.75	$70.80
Purchase #6	$189.92	10.217%	$209.3241	$209.32	$209.30	$209.30
Purchase #7	$71.82	8.800%	$78.1402	$78.14	$78.15	$78.10
7 purchase totals =	$1,011.72		$1,108.0749	$1,108.08	$1,108.05	$1,108.10