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	$196.68	4.464%	$205.4598	$205.46	$205.45	$205.50
Purchase #2	$56.76	8.200%	$61.4143	$61.41	$61.40	$61.40
Purchase #3	$122.61	9.692%	$134.4934	$134.49	$134.50	$134.50
Purchase #4	$217.63	5.456%	$229.5039	$229.50	$229.50	$229.50
Purchase #5	$85.46	4.825%	$89.5834	$89.58	$89.60	$89.60
Purchase #6	$146.28	6.525%	$155.8248	$155.82	$155.80	$155.80
Purchase #7	$116.89	12.432%	$131.4218	$131.42	$131.40	$131.40
7 purchase totals =	$942.31		$1,007.7014	$1,007.68	$1,007.65	$1,007.70