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	$147.72	7.539%	$158.8566	$158.86	$158.85	$158.90
Purchase #2	$138.85	10.867%	$153.9388	$153.94	$153.95	$153.90
Purchase #3	$209.33	13.836%	$238.2929	$238.29	$238.30	$238.30
Purchase #4	$137.89	4.460%	$144.0399	$144.04	$144.05	$144.00
Purchase #5	$123.39	4.772%	$129.2782	$129.28	$129.30	$129.30
Purchase #6	$47.75	9.261%	$52.1721	$52.17	$52.15	$52.20
Purchase #7	$218.59	7.430%	$234.8312	$234.83	$234.85	$234.80
7 purchase totals =	$1,023.52		$1,111.4097	$1,111.41	$1,111.45	$1,111.40