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	$234.38	3.726%	$243.113	$243.11	$243.10	$243.10
Purchase #2	$87.31	3.354%	$90.2384	$90.24	$90.25	$90.20
Purchase #3	$235.29	8.231%	$254.6567	$254.66	$254.65	$254.70
Purchase #4	$80.86	13.267%	$91.5877	$91.59	$91.60	$91.60
Purchase #5	$243.37	5.368%	$256.4341	$256.43	$256.45	$256.40
Purchase #6	$80.64	11.361%	$89.8015	$89.80	$89.80	$89.80
Purchase #7	$132.60	8.865%	$144.355	$144.36	$144.35	$144.40
7 purchase totals =	$1,094.45		$1,170.1864	$1,170.19	$1,170.20	$1,170.20