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	$198.29	3.336%	$204.905	$204.91	$204.90	$204.90
Purchase #2	$158.68	10.530%	$175.389	$175.39	$175.40	$175.40
Purchase #3	$233.33	7.212%	$250.1578	$250.16	$250.15	$250.20
Purchase #4	$191.65	9.207%	$209.2952	$209.30	$209.30	$209.30
Purchase #5	$83.89	11.838%	$93.8209	$93.82	$93.80	$93.80
Purchase #6	$69.44	13.504%	$78.8172	$78.82	$78.80	$78.80
Purchase #7	$110.30	5.242%	$116.0819	$116.08	$116.10	$116.10
7 purchase totals =	$1,045.58		$1,128.4670	$1,128.48	$1,128.45	$1,128.50