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	$86.69	6.825%	$92.6066	$92.61	$92.60	$92.60
Purchase #2	$47.74	3.345%	$49.3369	$49.34	$49.35	$49.30
Purchase #3	$168.45	4.132%	$175.4104	$175.41	$175.40	$175.40
Purchase #4	$235.79	6.225%	$250.4679	$250.47	$250.45	$250.50
Purchase #5	$231.44	13.810%	$263.4019	$263.40	$263.40	$263.40
Purchase #6	$243.39	13.186%	$275.4834	$275.48	$275.50	$275.50
Purchase #7	$20.44	3.112%	$21.0761	$21.08	$21.10	$21.10
7 purchase totals =	$1,033.94		$1,127.7832	$1,127.79	$1,127.80	$1,127.80