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	$178.63	9.274%	$195.1961	$195.20	$195.20	$195.20
Purchase #2	$158.95	5.222%	$167.2504	$167.25	$167.25	$167.30
Purchase #3	$209.43	13.374%	$237.4392	$237.44	$237.45	$237.40
Purchase #4	$91.52	8.810%	$99.5829	$99.58	$99.60	$99.60
Purchase #5	$85.97	10.330%	$94.8507	$94.85	$94.85	$94.90
Purchase #6	$28.45	13.817%	$32.3809	$32.38	$32.40	$32.40
Purchase #7	$178.83	6.641%	$190.7061	$190.71	$190.70	$190.70
7 purchase totals =	$931.78		$1,017.4063	$1,017.41	$1,017.45	$1,017.50