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	$82.59	10.658%	$91.3924	$91.39	$91.40	$91.40
Purchase #2	$230.25	5.682%	$243.3328	$243.33	$243.35	$243.30
Purchase #3	$172.33	11.154%	$191.5517	$191.55	$191.55	$191.60
Purchase #4	$228.55	13.760%	$259.9985	$260.00	$260.00	$260.00
Purchase #5	$242.55	10.226%	$267.3532	$267.35	$267.35	$267.40
Purchase #6	$196.31	13.531%	$222.8727	$222.87	$222.85	$222.90
Purchase #7	$98.68	7.155%	$105.7406	$105.74	$105.75	$105.70
7 purchase totals =	$1,251.26		$1,382.2419	$1,382.23	$1,382.25	$1,382.30