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	$214.77	13.327%	$243.3924	$243.39	$243.40	$243.40
Purchase #2	$77.27	6.129%	$82.0059	$82.01	$82.00	$82.00
Purchase #3	$19.31	6.722%	$20.608	$20.61	$20.60	$20.60
Purchase #4	$192.74	12.834%	$217.4763	$217.48	$217.50	$217.50
Purchase #5	$245.94	10.720%	$272.3048	$272.30	$272.30	$272.30
Purchase #6	$170.44	11.547%	$190.1207	$190.12	$190.10	$190.10
Purchase #7	$155.28	8.718%	$168.8173	$168.82	$168.80	$168.80
7 purchase totals =	$1,075.75		$1,194.7254	$1,194.73	$1,194.70	$1,194.70