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	$107.88	11.786%	$120.5947	$120.59	$120.60	$120.60
Purchase #2	$148.45	3.375%	$153.4602	$153.46	$153.45	$153.50
Purchase #3	$112.56	3.681%	$116.7033	$116.70	$116.70	$116.70
Purchase #4	$140.81	8.331%	$152.5409	$152.54	$152.55	$152.50
Purchase #5	$195.72	7.459%	$210.3188	$210.32	$210.30	$210.30
Purchase #6	$197.26	10.708%	$218.3826	$218.38	$218.40	$218.40
Purchase #7	$73.63	5.211%	$77.4669	$77.47	$77.45	$77.50
7 purchase totals =	$976.31		$1,049.4674	$1,049.46	$1,049.45	$1,049.50