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	$185.61	10.409%	$204.9301	$204.93	$204.95	$204.90
Purchase #2	$162.45	11.446%	$181.044	$181.04	$181.05	$181.00
Purchase #3	$74.96	4.541%	$78.3639	$78.36	$78.35	$78.40
Purchase #4	$233.27	10.672%	$258.1646	$258.16	$258.15	$258.20
Purchase #5	$177.47	4.740%	$185.8821	$185.88	$185.90	$185.90
Purchase #6	$200.66	4.466%	$209.6215	$209.62	$209.60	$209.60
Purchase #7	$47.61	12.346%	$53.4879	$53.49	$53.50	$53.50
7 purchase totals =	$1,082.03		$1,171.4941	$1,171.48	$1,171.50	$1,171.50