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	$146.77	4.442%	$153.2895	$153.29	$153.30	$153.30
Purchase #2	$239.86	3.374%	$247.9529	$247.95	$247.95	$248.00
Purchase #3	$42.58	4.399%	$44.4531	$44.45	$44.45	$44.50
Purchase #4	$209.92	11.551%	$234.1679	$234.17	$234.15	$234.20
Purchase #5	$42.33	10.690%	$46.8551	$46.86	$46.85	$46.90
Purchase #6	$92.75	8.592%	$100.7191	$100.72	$100.70	$100.70
Purchase #7	$100.30	9.259%	$109.5868	$109.59	$109.60	$109.60
7 purchase totals =	$874.51		$937.0244	$937.03	$937.00	$937.20