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	$91.77	5.360%	$96.6889	$96.69	$96.70	$96.70
Purchase #2	$86.45	6.503%	$92.0718	$92.07	$92.05	$92.10
Purchase #3	$20.89	6.166%	$22.1781	$22.18	$22.20	$22.20
Purchase #4	$78.34	9.864%	$86.0675	$86.07	$86.05	$86.10
Purchase #5	$131.60	3.478%	$136.177	$136.18	$136.20	$136.20
Purchase #6	$17.72	4.555%	$18.5271	$18.53	$18.55	$18.50
Purchase #7	$50.71	6.313%	$53.9113	$53.91	$53.90	$53.90
7 purchase totals =	$477.48		$505.6217	$505.63	$505.65	$505.70