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	$197.49	11.187%	$219.5832	$219.58	$219.60	$219.60
Purchase #2	$84.92	5.198%	$89.3341	$89.33	$89.35	$89.30
Purchase #3	$35.56	5.835%	$37.6349	$37.63	$37.65	$37.60
Purchase #4	$21.72	6.847%	$23.2072	$23.21	$23.20	$23.20
Purchase #5	$157.72	13.714%	$179.3497	$179.35	$179.35	$179.30
Purchase #6	$147.38	13.656%	$167.5062	$167.51	$167.50	$167.50
Purchase #7	$98.72	8.178%	$106.7933	$106.79	$106.80	$106.80
7 purchase totals =	$743.51		$823.4086	$823.40	$823.45	$823.30