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	$139.32	3.687%	$144.4567	$144.46	$144.45	$144.50
Purchase #2	$114.97	5.117%	$120.853	$120.85	$120.85	$120.90
Purchase #3	$31.27	7.469%	$33.6056	$33.61	$33.60	$33.60
Purchase #4	$243.66	9.222%	$266.1303	$266.13	$266.15	$266.10
Purchase #5	$233.41	12.770%	$263.2165	$263.22	$263.20	$263.20
Purchase #6	$48.27	11.813%	$53.9721	$53.97	$53.95	$54.00
Purchase #7	$60.61	6.289%	$64.4218	$64.42	$64.40	$64.40
7 purchase totals =	$871.51		$946.6560	$946.66	$946.60	$946.70