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	$188.86	6.205%	$200.5788	$200.58	$200.60	$200.60
Purchase #2	$40.32	8.344%	$43.6843	$43.68	$43.70	$43.70
Purchase #3	$215.69	10.332%	$237.9751	$237.98	$238.00	$238.00
Purchase #4	$62.58	7.489%	$67.2666	$67.27	$67.25	$67.30
Purchase #5	$172.59	10.373%	$190.4928	$190.49	$190.50	$190.50
Purchase #6	$213.78	10.118%	$235.4103	$235.41	$235.40	$235.40
Purchase #7	$92.57	7.312%	$99.3387	$99.34	$99.35	$99.30
7 purchase totals =	$986.39		$1,074.7466	$1,074.75	$1,074.80	$1,074.80