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	$173.96	10.630%	$192.4519	$192.45	$192.45	$192.50
Purchase #2	$38.73	10.433%	$42.7707	$42.77	$42.75	$42.80
Purchase #3	$95.57	5.867%	$101.1771	$101.18	$101.20	$101.20
Purchase #4	$104.55	4.489%	$109.2432	$109.24	$109.25	$109.20
Purchase #5	$65.41	9.801%	$71.8208	$71.82	$71.80	$71.80
Purchase #6	$195.44	7.117%	$209.3495	$209.35	$209.35	$209.30
Purchase #7	$66.52	8.817%	$72.3851	$72.39	$72.40	$72.40
7 purchase totals =	$740.18		$799.1983	$799.20	$799.20	$799.20