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	$35.58	4.813%	$37.2925	$37.29	$37.30	$37.30
Purchase #2	$11.70	9.166%	$12.7724	$12.77	$12.75	$12.80
Purchase #3	$168.75	6.329%	$179.4302	$179.43	$179.45	$179.40
Purchase #4	$200.28	8.678%	$217.6603	$217.66	$217.65	$217.70
Purchase #5	$102.51	11.747%	$114.5518	$114.55	$114.55	$114.60
Purchase #6	$230.69	6.377%	$245.4011	$245.40	$245.40	$245.40
Purchase #7	$105.47	5.456%	$111.2244	$111.22	$111.20	$111.20
7 purchase totals =	$854.98		$918.3327	$918.32	$918.30	$918.40