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	$162.66	6.180%	$172.7124	$172.71	$172.70	$172.70
Purchase #2	$55.56	10.209%	$61.2321	$61.23	$61.25	$61.20
Purchase #3	$181.79	9.148%	$198.4201	$198.42	$198.40	$198.40
Purchase #4	$242.68	3.770%	$251.829	$251.83	$251.85	$251.80
Purchase #5	$49.54	9.437%	$54.2151	$54.22	$54.20	$54.20
Purchase #6	$230.38	6.271%	$244.8271	$244.83	$244.85	$244.80
Purchase #7	$103.28	12.497%	$116.1869	$116.19	$116.20	$116.20
7 purchase totals =	$1,025.89		$1,099.4227	$1,099.43	$1,099.45	$1,099.30