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	$143.59	10.498%	$158.6641	$158.66	$158.65	$158.70
Purchase #2	$108.64	9.729%	$119.2096	$119.21	$119.20	$119.20
Purchase #3	$184.60	8.466%	$200.2282	$200.23	$200.25	$200.20
Purchase #4	$93.55	3.489%	$96.814	$96.81	$96.80	$96.80
Purchase #5	$178.73	5.644%	$188.8175	$188.82	$188.80	$188.80
Purchase #6	$138.79	9.709%	$152.2651	$152.27	$152.25	$152.30
Purchase #7	$36.69	5.240%	$38.6126	$38.61	$38.60	$38.60
7 purchase totals =	$884.59		$954.6111	$954.61	$954.55	$954.60