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	$125.37	4.520%	$131.0367	$131.04	$131.05	$131.00
Purchase #2	$173.76	11.221%	$193.2576	$193.26	$193.25	$193.30
Purchase #3	$250.42	7.193%	$268.4327	$268.43	$268.45	$268.40
Purchase #4	$230.52	10.611%	$254.9805	$254.98	$255.00	$255.00
Purchase #5	$19.93	8.834%	$21.6906	$21.69	$21.70	$21.70
Purchase #6	$147.77	11.756%	$165.1418	$165.14	$165.15	$165.10
Purchase #7	$28.94	10.359%	$31.9379	$31.94	$31.95	$31.90
7 purchase totals =	$976.71		$1,066.4778	$1,066.48	$1,066.55	$1,066.40