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	$40.99	11.661%	$45.7698	$45.77	$45.75	$45.80
Purchase #2	$250.36	11.555%	$279.2891	$279.29	$279.30	$279.30
Purchase #3	$195.59	11.217%	$217.5293	$217.53	$217.55	$217.50
Purchase #4	$142.52	10.846%	$157.9777	$157.98	$158.00	$158.00
Purchase #5	$49.73	10.111%	$54.7582	$54.76	$54.75	$54.80
Purchase #6	$200.92	4.239%	$209.437	$209.44	$209.45	$209.40
Purchase #7	$227.42	3.498%	$235.3752	$235.38	$235.40	$235.40
7 purchase totals =	$1,107.53		$1,200.1363	$1,200.15	$1,200.20	$1,200.20