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	$213.59	4.555%	$223.319	$223.32	$223.30	$223.30
Purchase #2	$129.78	11.748%	$145.0266	$145.03	$145.05	$145.00
Purchase #3	$69.36	3.153%	$71.5469	$71.55	$71.55	$71.50
Purchase #4	$75.96	9.359%	$83.0691	$83.07	$83.05	$83.10
Purchase #5	$211.66	8.313%	$229.2553	$229.26	$229.25	$229.30
Purchase #6	$196.55	10.124%	$216.4487	$216.45	$216.45	$216.40
Purchase #7	$161.25	11.494%	$179.7841	$179.78	$179.80	$179.80
7 purchase totals =	$1,058.15		$1,148.4497	$1,148.46	$1,148.45	$1,148.40