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	$160.62	7.391%	$172.4914	$172.49	$172.50	$172.50
Purchase #2	$57.58	3.593%	$59.6488	$59.65	$59.65	$59.60
Purchase #3	$80.27	12.771%	$90.5213	$90.52	$90.50	$90.50
Purchase #4	$238.34	4.355%	$248.7197	$248.72	$248.70	$248.70
Purchase #5	$86.92	5.618%	$91.8032	$91.80	$91.80	$91.80
Purchase #6	$114.56	4.266%	$119.4471	$119.45	$119.45	$119.40
Purchase #7	$249.86	5.849%	$264.4743	$264.47	$264.45	$264.50
7 purchase totals =	$988.15		$1,047.1058	$1,047.10	$1,047.05	$1,047.00