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	$133.62	10.653%	$147.8545	$147.85	$147.85	$147.90
Purchase #2	$94.51	10.688%	$104.6112	$104.61	$104.60	$104.60
Purchase #3	$137.55	3.519%	$142.3904	$142.39	$142.40	$142.40
Purchase #4	$10.98	7.164%	$11.7666	$11.77	$11.75	$11.80
Purchase #5	$132.36	11.247%	$147.2465	$147.25	$147.25	$147.20
Purchase #6	$83.62	7.107%	$89.5629	$89.56	$89.55	$89.60
Purchase #7	$223.69	13.312%	$253.4676	$253.47	$253.45	$253.50
7 purchase totals =	$816.33		$896.8997	$896.90	$896.85	$897.00