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	$43.76	6.768%	$46.7217	$46.72	$46.70	$46.70
Purchase #2	$153.32	11.717%	$171.2845	$171.28	$171.30	$171.30
Purchase #3	$247.43	8.500%	$268.4616	$268.46	$268.45	$268.50
Purchase #4	$87.88	13.183%	$99.4652	$99.47	$99.45	$99.50
Purchase #5	$237.84	3.497%	$246.1573	$246.16	$246.15	$246.20
Purchase #6	$105.57	3.808%	$109.5901	$109.59	$109.60	$109.60
Purchase #7	$134.90	10.491%	$149.0524	$149.05	$149.05	$149.10
7 purchase totals =	$1,010.70		$1,090.7328	$1,090.73	$1,090.70	$1,090.90