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	$157.64	5.210%	$165.853	$165.85	$165.85	$165.90
Purchase #2	$78.81	13.678%	$89.5896	$89.59	$89.60	$89.60
Purchase #3	$26.69	11.427%	$29.7399	$29.74	$29.75	$29.70
Purchase #4	$104.95	11.857%	$117.3939	$117.39	$117.40	$117.40
Purchase #5	$116.96	5.543%	$123.4431	$123.44	$123.45	$123.40
Purchase #6	$250.72	7.555%	$269.6619	$269.66	$269.65	$269.70
Purchase #7	$75.94	10.457%	$83.881	$83.88	$83.90	$83.90
7 purchase totals =	$811.71		$879.5624	$879.55	$879.60	$879.60