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	$54.90	9.135%	$59.9151	$59.92	$59.90	$59.90
Purchase #2	$34.68	9.329%	$37.9153	$37.92	$37.90	$37.90
Purchase #3	$148.65	11.625%	$165.9306	$165.93	$165.95	$165.90
Purchase #4	$116.56	8.868%	$126.8965	$126.90	$126.90	$126.90
Purchase #5	$180.27	5.267%	$189.7648	$189.76	$189.75	$189.80
Purchase #6	$194.30	7.578%	$209.0241	$209.02	$209.00	$209.00
Purchase #7	$248.70	11.653%	$277.681	$277.68	$277.70	$277.70
7 purchase totals =	$978.06		$1,067.1274	$1,067.13	$1,067.10	$1,067.10