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	$198.67	6.317%	$211.22	$211.22	$211.20	$211.20
Purchase #2	$41.41	10.371%	$45.7046	$45.70	$45.70	$45.70
Purchase #3	$20.81	3.607%	$21.5606	$21.56	$21.55	$21.60
Purchase #4	$68.36	6.597%	$72.8697	$72.87	$72.85	$72.90
Purchase #5	$68.79	10.692%	$76.145	$76.15	$76.15	$76.10
Purchase #6	$46.98	3.471%	$48.6107	$48.61	$48.60	$48.60
Purchase #7	$75.41	13.221%	$85.38	$85.38	$85.40	$85.40
7 purchase totals =	$520.43		$561.4906	$561.49	$561.45	$561.50