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	$94.83	7.179%	$101.6378	$101.64	$101.65	$101.60
Purchase #2	$151.43	5.874%	$160.325	$160.33	$160.35	$160.30
Purchase #3	$170.86	11.252%	$190.0852	$190.09	$190.10	$190.10
Purchase #4	$96.77	3.137%	$99.8057	$99.81	$99.80	$99.80
Purchase #5	$71.50	3.285%	$73.8488	$73.85	$73.85	$73.80
Purchase #6	$191.52	4.764%	$200.644	$200.64	$200.65	$200.60
Purchase #7	$56.90	3.205%	$58.7236	$58.72	$58.70	$58.70
7 purchase totals =	$833.81		$885.0701	$885.08	$885.10	$884.90