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	$236.34	11.495%	$263.5073	$263.51	$263.50	$263.50
Purchase #2	$49.40	11.146%	$54.9061	$54.91	$54.90	$54.90
Purchase #3	$207.72	6.421%	$221.0577	$221.06	$221.05	$221.10
Purchase #4	$82.77	3.327%	$85.5238	$85.52	$85.50	$85.50
Purchase #5	$118.27	8.631%	$128.4779	$128.48	$128.50	$128.50
Purchase #6	$245.84	3.450%	$254.3215	$254.32	$254.30	$254.30
Purchase #7	$30.34	13.873%	$34.5491	$34.55	$34.55	$34.50
7 purchase totals =	$970.68		$1,042.3434	$1,042.35	$1,042.30	$1,042.30