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	$73.90	5.754%	$78.1522	$78.15	$78.15	$78.20
Purchase #2	$37.68	7.358%	$40.4525	$40.45	$40.45	$40.50
Purchase #3	$47.43	12.550%	$53.3825	$53.38	$53.40	$53.40
Purchase #4	$217.98	11.124%	$242.2281	$242.23	$242.25	$242.20
Purchase #5	$209.37	3.766%	$217.2549	$217.25	$217.25	$217.30
Purchase #6	$108.47	10.763%	$120.1446	$120.14	$120.15	$120.10
Purchase #7	$248.87	6.248%	$264.4194	$264.42	$264.40	$264.40
7 purchase totals =	$943.70		$1,016.0342	$1,016.02	$1,016.05	$1,016.10