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	$89.89	11.339%	$100.0826	$100.08	$100.10	$100.10
Purchase #2	$95.92	8.565%	$104.1355	$104.14	$104.15	$104.10
Purchase #3	$74.49	4.829%	$78.0871	$78.09	$78.10	$78.10
Purchase #4	$149.63	7.797%	$161.2967	$161.30	$161.30	$161.30
Purchase #5	$167.91	4.196%	$174.9555	$174.96	$174.95	$175.00
Purchase #6	$53.59	5.386%	$56.4764	$56.48	$56.50	$56.50
Purchase #7	$153.58	7.623%	$165.2874	$165.29	$165.30	$165.30
7 purchase totals =	$785.01		$840.3212	$840.34	$840.40	$840.40