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	$141.76	8.143%	$153.3035	$153.30	$153.30	$153.30
Purchase #2	$94.87	10.145%	$104.4946	$104.49	$104.50	$104.50
Purchase #3	$191.44	12.344%	$215.0714	$215.07	$215.05	$215.10
Purchase #4	$30.56	7.617%	$32.8878	$32.89	$32.90	$32.90
Purchase #5	$139.98	10.270%	$154.3559	$154.36	$154.35	$154.40
Purchase #6	$147.27	12.238%	$165.2929	$165.29	$165.30	$165.30
Purchase #7	$229.86	6.804%	$245.4997	$245.50	$245.50	$245.50
7 purchase totals =	$975.74		$1,070.9058	$1,070.90	$1,070.90	$1,071.00