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	$133.25	8.650%	$144.7761	$144.78	$144.80	$144.80
Purchase #2	$136.54	6.346%	$145.2048	$145.20	$145.20	$145.20
Purchase #3	$109.79	4.440%	$114.6647	$114.66	$114.65	$114.70
Purchase #4	$69.61	4.784%	$72.9401	$72.94	$72.95	$72.90
Purchase #5	$250.98	5.388%	$264.5028	$264.50	$264.50	$264.50
Purchase #6	$189.92	10.207%	$209.3051	$209.31	$209.30	$209.30
Purchase #7	$133.52	11.197%	$148.4702	$148.47	$148.45	$148.50
7 purchase totals =	$1,023.61		$1,099.8638	$1,099.86	$1,099.85	$1,099.90