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	$202.27	13.252%	$229.0748	$229.07	$229.05	$229.10
Purchase #2	$196.47	7.333%	$210.8771	$210.88	$210.90	$210.90
Purchase #3	$65.35	8.555%	$70.9407	$70.94	$70.95	$70.90
Purchase #4	$169.41	13.471%	$192.2312	$192.23	$192.25	$192.20
Purchase #5	$41.46	3.403%	$42.8709	$42.87	$42.85	$42.90
Purchase #6	$80.63	11.106%	$89.5848	$89.58	$89.60	$89.60
Purchase #7	$47.47	9.650%	$52.0509	$52.05	$52.05	$52.10
7 purchase totals =	$803.06		$887.6304	$887.62	$887.65	$887.70