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	$62.76	7.215%	$67.2881	$67.29	$67.30	$67.30
Purchase #2	$24.85	11.338%	$27.6675	$27.67	$27.65	$27.70
Purchase #3	$247.87	9.866%	$272.3249	$272.32	$272.30	$272.30
Purchase #4	$247.27	6.539%	$263.439	$263.44	$263.45	$263.40
Purchase #5	$76.43	6.796%	$81.6242	$81.62	$81.60	$81.60
Purchase #6	$243.55	10.272%	$268.5675	$268.57	$268.55	$268.60
Purchase #7	$244.54	12.822%	$275.8949	$275.89	$275.90	$275.90
7 purchase totals =	$1,147.27		$1,256.8061	$1,256.80	$1,256.75	$1,256.80