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	$140.30	3.396%	$145.0646	$145.06	$145.05	$145.10
Purchase #2	$224.35	8.510%	$243.4422	$243.44	$243.45	$243.40
Purchase #3	$171.83	7.106%	$184.0402	$184.04	$184.05	$184.00
Purchase #4	$167.57	10.551%	$185.2503	$185.25	$185.25	$185.30
Purchase #5	$84.75	13.708%	$96.3675	$96.37	$96.35	$96.40
Purchase #6	$194.49	7.246%	$208.5827	$208.58	$208.60	$208.60
Purchase #7	$33.57	11.830%	$37.5413	$37.54	$37.55	$37.50
7 purchase totals =	$1,016.86		$1,100.2888	$1,100.28	$1,100.30	$1,100.30