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	$181.36	10.690%	$200.7474	$200.75	$200.75	$200.70
Purchase #2	$189.32	5.400%	$199.5433	$199.54	$199.55	$199.50
Purchase #3	$9.48	7.161%	$10.1589	$10.16	$10.15	$10.20
Purchase #4	$140.46	7.708%	$151.2867	$151.29	$151.30	$151.30
Purchase #5	$135.77	10.781%	$150.4074	$150.41	$150.40	$150.40
Purchase #6	$32.87	6.254%	$34.9257	$34.93	$34.95	$34.90
Purchase #7	$80.43	3.526%	$83.266	$83.27	$83.25	$83.30
7 purchase totals =	$769.69		$830.3354	$830.35	$830.35	$830.30