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	$179.82	3.263%	$185.6875	$185.69	$185.70	$185.70
Purchase #2	$116.89	9.449%	$127.9349	$127.93	$127.95	$127.90
Purchase #3	$149.54	10.789%	$165.6739	$165.67	$165.65	$165.70
Purchase #4	$227.55	3.426%	$235.3459	$235.35	$235.35	$235.30
Purchase #5	$242.36	13.288%	$274.5648	$274.56	$274.55	$274.60
Purchase #6	$38.26	5.820%	$40.4867	$40.49	$40.50	$40.50
Purchase #7	$229.95	5.663%	$242.9721	$242.97	$242.95	$243.00
7 purchase totals =	$1,184.37		$1,272.6658	$1,272.66	$1,272.65	$1,272.70