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	$43.41	4.521%	$45.3726	$45.37	$45.35	$45.40
Purchase #2	$103.63	7.379%	$111.2769	$111.28	$111.30	$111.30
Purchase #3	$167.31	13.598%	$190.0608	$190.06	$190.05	$190.10
Purchase #4	$238.29	5.865%	$252.2657	$252.27	$252.25	$252.30
Purchase #5	$215.40	3.644%	$223.2492	$223.25	$223.25	$223.20
Purchase #6	$133.79	11.654%	$149.3819	$149.38	$149.40	$149.40
Purchase #7	$56.61	12.498%	$63.6851	$63.69	$63.70	$63.70
7 purchase totals =	$958.44		$1,035.2922	$1,035.30	$1,035.30	$1,035.40