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	$84.47	3.377%	$87.3226	$87.32	$87.30	$87.30
Purchase #2	$39.34	11.597%	$43.9023	$43.90	$43.90	$43.90
Purchase #3	$237.97	7.328%	$255.4084	$255.41	$255.40	$255.40
Purchase #4	$46.43	4.784%	$48.6512	$48.65	$48.65	$48.70
Purchase #5	$25.65	10.259%	$28.2814	$28.28	$28.30	$28.30
Purchase #6	$157.27	11.532%	$175.4064	$175.41	$175.40	$175.40
Purchase #7	$188.74	4.263%	$196.786	$196.79	$196.80	$196.80
7 purchase totals =	$779.87		$835.7583	$835.76	$835.75	$835.80