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	$114.36	11.832%	$127.8911	$127.89	$127.90	$127.90
Purchase #2	$37.44	6.292%	$39.7957	$39.80	$39.80	$39.80
Purchase #3	$70.47	10.113%	$77.5966	$77.60	$77.60	$77.60
Purchase #4	$88.26	12.340%	$99.1513	$99.15	$99.15	$99.20
Purchase #5	$223.47	4.398%	$233.2982	$233.30	$233.30	$233.30
Purchase #6	$239.78	13.143%	$271.2943	$271.29	$271.30	$271.30
Purchase #7	$221.42	4.840%	$232.1367	$232.14	$232.15	$232.10
7 purchase totals =	$995.20		$1,081.1639	$1,081.17	$1,081.20	$1,081.20