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	$242.75	5.629%	$256.4144	$256.41	$256.40	$256.40
Purchase #2	$160.69	6.847%	$171.6924	$171.69	$171.70	$171.70
Purchase #3	$126.41	11.595%	$141.0672	$141.07	$141.05	$141.10
Purchase #4	$99.91	12.217%	$112.116	$112.12	$112.10	$112.10
Purchase #5	$158.75	8.572%	$172.3581	$172.36	$172.35	$172.40
Purchase #6	$190.30	10.203%	$209.7163	$209.72	$209.70	$209.70
Purchase #7	$115.61	5.737%	$122.2425	$122.24	$122.25	$122.20
7 purchase totals =	$1,094.42		$1,185.6069	$1,185.61	$1,185.55	$1,185.60