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	$98.48	11.372%	$109.6791	$109.68	$109.70	$109.70
Purchase #2	$92.46	13.760%	$105.1825	$105.18	$105.20	$105.20
Purchase #3	$40.54	9.472%	$44.3799	$44.38	$44.40	$44.40
Purchase #4	$85.51	9.716%	$93.8182	$93.82	$93.80	$93.80
Purchase #5	$154.46	11.353%	$171.9958	$172.00	$172.00	$172.00
Purchase #6	$142.93	6.751%	$152.5792	$152.58	$152.60	$152.60
Purchase #7	$90.29	10.407%	$99.6865	$99.69	$99.70	$99.70
7 purchase totals =	$704.67		$777.3212	$777.33	$777.40	$777.40