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	$151.43	5.811%	$160.2296	$160.23	$160.25	$160.20
Purchase #2	$174.93	9.143%	$190.9238	$190.92	$190.90	$190.90
Purchase #3	$53.25	13.639%	$60.5128	$60.51	$60.50	$60.50
Purchase #4	$73.86	3.507%	$76.4503	$76.45	$76.45	$76.50
Purchase #5	$104.67	7.516%	$112.537	$112.54	$112.55	$112.50
Purchase #6	$170.51	6.308%	$181.2658	$181.27	$181.25	$181.30
Purchase #7	$245.43	12.185%	$275.3356	$275.34	$275.35	$275.30
7 purchase totals =	$974.08		$1,057.2549	$1,057.26	$1,057.25	$1,057.20