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	$216.35	5.788%	$228.8723	$228.87	$228.85	$228.90
Purchase #2	$70.32	3.488%	$72.7728	$72.77	$72.75	$72.80
Purchase #3	$175.77	8.569%	$190.8317	$190.83	$190.85	$190.80
Purchase #4	$156.73	10.785%	$173.6333	$173.63	$173.65	$173.60
Purchase #5	$25.88	10.819%	$28.68	$28.68	$28.70	$28.70
Purchase #6	$128.87	6.836%	$137.6796	$137.68	$137.70	$137.70
Purchase #7	$166.89	7.793%	$179.8957	$179.90	$179.90	$179.90
7 purchase totals =	$940.81		$1,012.3654	$1,012.36	$1,012.40	$1,012.40