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	$163.52	6.440%	$174.0507	$174.05	$174.05	$174.10
Purchase #2	$196.53	10.192%	$216.5603	$216.56	$216.55	$216.60
Purchase #3	$77.72	11.736%	$86.8412	$86.84	$86.85	$86.80
Purchase #4	$210.49	11.434%	$234.5574	$234.56	$234.55	$234.60
Purchase #5	$214.38	6.547%	$228.4155	$228.42	$228.40	$228.40
Purchase #6	$172.98	13.793%	$196.8391	$196.84	$196.85	$196.80
Purchase #7	$235.39	8.434%	$255.2428	$255.24	$255.25	$255.20
7 purchase totals =	$1,271.01		$1,392.5070	$1,392.51	$1,392.50	$1,392.50