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	$63.30	7.295%	$67.9177	$67.92	$67.90	$67.90
Purchase #2	$33.44	11.846%	$37.4013	$37.40	$37.40	$37.40
Purchase #3	$105.92	11.644%	$118.2533	$118.25	$118.25	$118.30
Purchase #4	$115.82	8.607%	$125.7886	$125.79	$125.80	$125.80
Purchase #5	$183.52	4.544%	$191.8591	$191.86	$191.85	$191.90
Purchase #6	$250.32	7.693%	$269.5771	$269.58	$269.60	$269.60
Purchase #7	$99.74	6.184%	$105.9079	$105.91	$105.90	$105.90
7 purchase totals =	$852.06		$916.7050	$916.71	$916.70	$916.80