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	$144.27	4.482%	$150.7362	$150.74	$150.75	$150.70
Purchase #2	$232.53	9.872%	$255.4854	$255.49	$255.50	$255.50
Purchase #3	$105.94	13.272%	$120.0004	$120.00	$120.00	$120.00
Purchase #4	$152.69	13.647%	$173.5276	$173.53	$173.55	$173.50
Purchase #5	$192.76	3.749%	$199.9866	$199.99	$200.00	$200.00
Purchase #6	$37.60	10.483%	$41.5416	$41.54	$41.55	$41.50
Purchase #7	$139.69	3.403%	$144.4437	$144.44	$144.45	$144.40
7 purchase totals =	$1,005.48		$1,085.7215	$1,085.73	$1,085.80	$1,085.60