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	$16.92	12.837%	$19.092	$19.09	$19.10	$19.10
Purchase #2	$31.89	4.410%	$33.2963	$33.30	$33.30	$33.30
Purchase #3	$8.64	11.686%	$9.6497	$9.65	$9.65	$9.60
Purchase #4	$135.89	9.315%	$148.5482	$148.55	$148.55	$148.50
Purchase #5	$48.42	7.600%	$52.0999	$52.10	$52.10	$52.10
Purchase #6	$63.37	13.813%	$72.1233	$72.12	$72.10	$72.10
Purchase #7	$94.76	6.472%	$100.8929	$100.89	$100.90	$100.90
7 purchase totals =	$399.89		$435.7023	$435.70	$435.70	$435.60