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	$59.99	9.185%	$65.5001	$65.50	$65.50	$65.50
Purchase #2	$46.59	6.117%	$49.4399	$49.44	$49.45	$49.40
Purchase #3	$60.92	6.767%	$65.0425	$65.04	$65.05	$65.00
Purchase #4	$16.92	3.683%	$17.5432	$17.54	$17.55	$17.50
Purchase #5	$89.27	6.790%	$95.3314	$95.33	$95.35	$95.30
Purchase #6	$63.81	12.239%	$71.6197	$71.62	$71.60	$71.60
Purchase #7	$105.64	13.712%	$120.1254	$120.13	$120.15	$120.10
7 purchase totals =	$443.14		$484.6022	$484.60	$484.65	$484.40