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	$34.71	6.661%	$37.022	$37.02	$37.00	$37.00
Purchase #2	$40.68	10.774%	$45.0629	$45.06	$45.05	$45.10
Purchase #3	$38.64	9.140%	$42.1717	$42.17	$42.15	$42.20
Purchase #4	$75.59	4.165%	$78.7383	$78.74	$78.75	$78.70
Purchase #5	$138.83	10.167%	$152.9448	$152.94	$152.95	$152.90
Purchase #6	$17.36	10.198%	$19.1304	$19.13	$19.15	$19.10
Purchase #7	$78.27	13.748%	$89.0306	$89.03	$89.05	$89.00
7 purchase totals =	$424.08		$464.1007	$464.09	$464.10	$464.00