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	$165.42	9.602%	$181.3036	$181.30	$181.30	$181.30
Purchase #2	$35.83	12.657%	$40.365	$40.37	$40.35	$40.40
Purchase #3	$63.58	13.859%	$72.3916	$72.39	$72.40	$72.40
Purchase #4	$197.35	9.584%	$216.264	$216.26	$216.25	$216.30
Purchase #5	$26.38	6.619%	$28.1261	$28.13	$28.15	$28.10
Purchase #6	$98.39	9.282%	$107.5226	$107.52	$107.50	$107.50
Purchase #7	$181.95	10.420%	$200.9092	$200.91	$200.90	$200.90
7 purchase totals =	$768.90		$846.8821	$846.88	$846.85	$846.90