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	$230.25	10.371%	$254.1292	$254.13	$254.15	$254.10
Purchase #2	$137.80	6.844%	$147.231	$147.23	$147.25	$147.20
Purchase #3	$73.85	7.825%	$79.6288	$79.63	$79.65	$79.60
Purchase #4	$80.59	10.439%	$89.0028	$89.00	$89.00	$89.00
Purchase #5	$203.45	11.549%	$226.9464	$226.95	$226.95	$226.90
Purchase #6	$94.46	6.439%	$100.5423	$100.54	$100.55	$100.50
Purchase #7	$148.43	10.231%	$163.6159	$163.62	$163.60	$163.60
7 purchase totals =	$968.83		$1,061.0964	$1,061.10	$1,061.15	$1,060.90