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	$55.28	6.751%	$59.012	$59.01	$59.00	$59.00
Purchase #2	$185.26	13.636%	$210.5221	$210.52	$210.50	$210.50
Purchase #3	$228.32	13.219%	$258.5016	$258.50	$258.50	$258.50
Purchase #4	$187.82	3.351%	$194.1138	$194.11	$194.10	$194.10
Purchase #5	$172.85	13.731%	$196.584	$196.58	$196.60	$196.60
Purchase #6	$53.78	12.109%	$60.2922	$60.29	$60.30	$60.30
Purchase #7	$64.88	12.848%	$73.2158	$73.22	$73.20	$73.20
7 purchase totals =	$948.19		$1,052.2415	$1,052.23	$1,052.20	$1,052.20