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	$45.85	10.550%	$50.6872	$50.69	$50.70	$50.70
Purchase #2	$53.56	11.798%	$59.879	$59.88	$59.90	$59.90
Purchase #3	$107.90	12.483%	$121.3692	$121.37	$121.35	$121.40
Purchase #4	$57.49	6.499%	$61.2263	$61.23	$61.25	$61.20
Purchase #5	$242.71	8.635%	$263.668	$263.67	$263.65	$263.70
Purchase #6	$154.68	3.715%	$160.4264	$160.43	$160.45	$160.40
Purchase #7	$81.71	9.809%	$89.7249	$89.72	$89.70	$89.70
7 purchase totals =	$743.90		$806.9810	$806.99	$807.00	$807.00