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	$65.32	9.598%	$71.5894	$71.59	$71.60	$71.60
Purchase #2	$89.35	10.430%	$98.6692	$98.67	$98.65	$98.70
Purchase #3	$40.32	7.496%	$43.3424	$43.34	$43.35	$43.30
Purchase #4	$72.80	8.461%	$78.9596	$78.96	$78.95	$79.00
Purchase #5	$121.80	9.788%	$133.7218	$133.72	$133.70	$133.70
Purchase #6	$242.74	5.122%	$255.1731	$255.17	$255.15	$255.20
Purchase #7	$115.40	10.658%	$127.6993	$127.70	$127.70	$127.70
7 purchase totals =	$747.73		$809.1548	$809.15	$809.10	$809.20