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	$105.82	11.568%	$118.0613	$118.06	$118.05	$118.10
Purchase #2	$65.40	10.303%	$72.1382	$72.14	$72.15	$72.10
Purchase #3	$172.82	8.766%	$187.9694	$187.97	$187.95	$188.00
Purchase #4	$58.61	10.668%	$64.8625	$64.86	$64.85	$64.90
Purchase #5	$153.67	11.376%	$171.1515	$171.15	$171.15	$171.20
Purchase #6	$46.27	10.785%	$51.2602	$51.26	$51.25	$51.30
Purchase #7	$231.86	11.311%	$258.0857	$258.09	$258.10	$258.10
7 purchase totals =	$834.45		$923.5288	$923.53	$923.50	$923.70