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	$95.97	7.389%	$103.0612	$103.06	$103.05	$103.10
Purchase #2	$125.85	13.381%	$142.69	$142.69	$142.70	$142.70
Purchase #3	$172.84	5.430%	$182.2252	$182.23	$182.25	$182.20
Purchase #4	$18.27	12.341%	$20.5247	$20.52	$20.50	$20.50
Purchase #5	$21.65	12.313%	$24.3158	$24.32	$24.30	$24.30
Purchase #6	$54.62	6.355%	$58.0911	$58.09	$58.10	$58.10
Purchase #7	$62.28	3.602%	$64.5233	$64.52	$64.50	$64.50
7 purchase totals =	$551.48		$595.4313	$595.43	$595.40	$595.40