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	$51.60	12.126%	$57.857	$57.86	$57.85	$57.90
Purchase #2	$60.98	4.870%	$63.9497	$63.95	$63.95	$63.90
Purchase #3	$238.67	3.673%	$247.4363	$247.44	$247.45	$247.40
Purchase #4	$188.82	13.432%	$214.1823	$214.18	$214.20	$214.20
Purchase #5	$218.34	12.110%	$244.781	$244.78	$244.80	$244.80
Purchase #6	$156.63	5.578%	$165.3668	$165.37	$165.35	$165.40
Purchase #7	$99.78	9.824%	$109.5824	$109.58	$109.60	$109.60
7 purchase totals =	$1,014.82		$1,103.1555	$1,103.16	$1,103.20	$1,103.20