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	$58.90	3.590%	$61.0145	$61.01	$61.00	$61.00
Purchase #2	$92.49	6.289%	$98.3067	$98.31	$98.30	$98.30
Purchase #3	$243.80	10.443%	$269.26	$269.26	$269.25	$269.30
Purchase #4	$20.27	4.767%	$21.2363	$21.24	$21.25	$21.20
Purchase #5	$157.78	4.714%	$165.2177	$165.22	$165.20	$165.20
Purchase #6	$7.27	7.675%	$7.828	$7.83	$7.85	$7.80
Purchase #7	$165.92	8.662%	$180.292	$180.29	$180.30	$180.30
7 purchase totals =	$746.43		$803.1552	$803.16	$803.15	$803.10