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	$145.78	5.227%	$153.3999	$153.40	$153.40	$153.40
Purchase #2	$246.80	13.689%	$280.5845	$280.58	$280.60	$280.60
Purchase #3	$139.54	4.834%	$146.2854	$146.29	$146.30	$146.30
Purchase #4	$180.48	4.520%	$188.6377	$188.64	$188.65	$188.60
Purchase #5	$182.89	3.722%	$189.6972	$189.70	$189.70	$189.70
Purchase #6	$149.50	3.865%	$155.2782	$155.28	$155.30	$155.30
Purchase #7	$48.97	12.826%	$55.2509	$55.25	$55.25	$55.30
7 purchase totals =	$1,093.96		$1,169.1338	$1,169.14	$1,169.20	$1,169.20