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	$86.64	7.377%	$93.0314	$93.03	$93.05	$93.00
Purchase #2	$127.99	12.381%	$143.8364	$143.84	$143.85	$143.80
Purchase #3	$164.91	11.779%	$184.3347	$184.33	$184.35	$184.30
Purchase #4	$161.83	12.640%	$182.2853	$182.29	$182.30	$182.30
Purchase #5	$196.73	13.301%	$222.8971	$222.90	$222.90	$222.90
Purchase #6	$228.64	10.788%	$253.3057	$253.31	$253.30	$253.30
Purchase #7	$199.88	9.236%	$218.3409	$218.34	$218.35	$218.30
7 purchase totals =	$1,166.62		$1,298.0315	$1,298.04	$1,298.10	$1,297.90