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	$203.67	9.480%	$222.9779	$222.98	$223.00	$223.00
Purchase #2	$41.52	9.330%	$45.3938	$45.39	$45.40	$45.40
Purchase #3	$65.77	7.430%	$70.6567	$70.66	$70.65	$70.70
Purchase #4	$137.53	9.616%	$150.7549	$150.75	$150.75	$150.80
Purchase #5	$98.49	7.234%	$105.6148	$105.61	$105.60	$105.60
Purchase #6	$42.43	9.684%	$46.5389	$46.54	$46.55	$46.50
Purchase #7	$118.49	9.793%	$130.0937	$130.09	$130.10	$130.10
7 purchase totals =	$707.90		$772.0307	$772.02	$772.05	$772.10