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	$188.98	4.188%	$196.8945	$196.89	$196.90	$196.90
Purchase #2	$53.84	6.510%	$57.345	$57.35	$57.35	$57.30
Purchase #3	$118.61	9.212%	$129.5364	$129.54	$129.55	$129.50
Purchase #4	$10.79	9.349%	$11.7988	$11.80	$11.80	$11.80
Purchase #5	$18.51	9.603%	$20.2875	$20.29	$20.30	$20.30
Purchase #6	$216.80	4.646%	$226.8725	$226.87	$226.85	$226.90
Purchase #7	$28.79	9.164%	$31.4283	$31.43	$31.45	$31.40
7 purchase totals =	$636.32		$674.1630	$674.17	$674.20	$674.10