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	$59.27	3.439%	$61.3083	$61.31	$61.30	$61.30
Purchase #2	$180.49	7.590%	$194.1892	$194.19	$194.20	$194.20
Purchase #3	$127.52	10.393%	$140.7732	$140.77	$140.75	$140.80
Purchase #4	$180.68	4.142%	$188.1638	$188.16	$188.15	$188.20
Purchase #5	$151.90	10.791%	$168.2915	$168.29	$168.30	$168.30
Purchase #6	$189.43	10.412%	$209.1535	$209.15	$209.15	$209.20
Purchase #7	$131.53	12.403%	$147.8437	$147.84	$147.85	$147.80
7 purchase totals =	$1,020.82		$1,109.7232	$1,109.71	$1,109.70	$1,109.80