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	$217.76	13.155%	$246.4063	$246.41	$246.40	$246.40
Purchase #2	$85.33	3.818%	$88.5879	$88.59	$88.60	$88.60
Purchase #3	$32.53	3.535%	$33.6799	$33.68	$33.70	$33.70
Purchase #4	$89.33	5.743%	$94.4602	$94.46	$94.45	$94.50
Purchase #5	$58.73	6.633%	$62.6256	$62.63	$62.65	$62.60
Purchase #6	$229.88	11.296%	$255.8472	$255.85	$255.85	$255.80
Purchase #7	$77.64	11.723%	$86.7417	$86.74	$86.75	$86.70
7 purchase totals =	$791.20		$868.3488	$868.36	$868.40	$868.30