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	$97.35	9.311%	$106.4143	$106.41	$106.40	$106.40
Purchase #2	$48.93	9.442%	$53.55	$53.55	$53.55	$53.60
Purchase #3	$91.25	10.109%	$100.4745	$100.47	$100.45	$100.50
Purchase #4	$231.97	13.145%	$262.4625	$262.46	$262.45	$262.50
Purchase #5	$7.59	8.435%	$8.2302	$8.23	$8.25	$8.20
Purchase #6	$81.92	9.727%	$89.8884	$89.89	$89.90	$89.90
Purchase #7	$97.39	5.834%	$103.0717	$103.07	$103.05	$103.10
7 purchase totals =	$656.40		$724.0916	$724.08	$724.05	$724.20