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	$41.51	9.502%	$45.4543	$45.45	$45.45	$45.50
Purchase #2	$179.39	12.593%	$201.9806	$201.98	$202.00	$202.00
Purchase #3	$227.71	6.149%	$241.7119	$241.71	$241.70	$241.70
Purchase #4	$250.49	5.717%	$264.8105	$264.81	$264.80	$264.80
Purchase #5	$122.59	4.314%	$127.8785	$127.88	$127.90	$127.90
Purchase #6	$172.33	8.726%	$187.3675	$187.37	$187.35	$187.40
Purchase #7	$123.31	5.672%	$130.3041	$130.30	$130.30	$130.30
7 purchase totals =	$1,117.33		$1,199.5074	$1,199.50	$1,199.50	$1,199.60