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	$62.68	8.259%	$67.8567	$67.86	$67.85	$67.90
Purchase #2	$87.80	7.477%	$94.3648	$94.36	$94.35	$94.40
Purchase #3	$101.27	4.486%	$105.813	$105.81	$105.80	$105.80
Purchase #4	$103.38	8.558%	$112.2273	$112.23	$112.25	$112.20
Purchase #5	$225.64	11.212%	$250.9388	$250.94	$250.95	$250.90
Purchase #6	$226.53	13.279%	$256.6109	$256.61	$256.60	$256.60
Purchase #7	$5.76	12.655%	$6.4889	$6.49	$6.50	$6.50
7 purchase totals =	$813.06		$894.3004	$894.30	$894.30	$894.30