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	$42.33	9.732%	$46.4496	$46.45	$46.45	$46.40
Purchase #2	$209.95	4.716%	$219.8512	$219.85	$219.85	$219.90
Purchase #3	$96.62	3.130%	$99.6442	$99.64	$99.65	$99.60
Purchase #4	$85.25	5.469%	$89.9123	$89.91	$89.90	$89.90
Purchase #5	$208.57	13.346%	$236.4058	$236.41	$236.40	$236.40
Purchase #6	$173.44	5.191%	$182.4433	$182.44	$182.45	$182.40
Purchase #7	$117.87	8.294%	$127.6461	$127.65	$127.65	$127.60
7 purchase totals =	$934.03		$1,002.3525	$1,002.35	$1,002.35	$1,002.20