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	$181.47	10.391%	$200.3265	$200.33	$200.35	$200.30
Purchase #2	$201.91	7.226%	$216.5	$216.50	$216.50	$216.50
Purchase #3	$68.44	10.316%	$75.5003	$75.50	$75.50	$75.50
Purchase #4	$61.54	10.377%	$67.926	$67.93	$67.95	$67.90
Purchase #5	$32.76	4.782%	$34.3266	$34.33	$34.35	$34.30
Purchase #6	$241.80	11.779%	$270.2816	$270.28	$270.30	$270.30
Purchase #7	$59.84	12.176%	$67.1261	$67.13	$67.15	$67.10
7 purchase totals =	$847.76		$931.9871	$932.00	$932.10	$931.90