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	$197.91	10.351%	$218.3957	$218.40	$218.40	$218.40
Purchase #2	$78.88	13.368%	$89.4247	$89.42	$89.40	$89.40
Purchase #3	$81.43	10.114%	$89.6658	$89.67	$89.65	$89.70
Purchase #4	$228.29	5.598%	$241.0697	$241.07	$241.05	$241.10
Purchase #5	$160.39	13.649%	$182.2816	$182.28	$182.30	$182.30
Purchase #6	$141.49	7.176%	$151.6433	$151.64	$151.65	$151.60
Purchase #7	$61.37	11.729%	$68.5681	$68.57	$68.55	$68.60
7 purchase totals =	$949.76		$1,041.0489	$1,041.05	$1,041.00	$1,041.10