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	$75.58	8.642%	$82.1116	$82.11	$82.10	$82.10
Purchase #2	$53.97	10.718%	$59.7545	$59.75	$59.75	$59.80
Purchase #3	$139.86	7.742%	$150.688	$150.69	$150.70	$150.70
Purchase #4	$133.97	7.185%	$143.5957	$143.60	$143.60	$143.60
Purchase #5	$157.83	5.438%	$166.4128	$166.41	$166.40	$166.40
Purchase #6	$247.36	5.827%	$261.7737	$261.77	$261.75	$261.80
Purchase #7	$218.32	13.299%	$247.3544	$247.35	$247.35	$247.40
7 purchase totals =	$1,026.89		$1,111.6907	$1,111.68	$1,111.65	$1,111.80