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	$144.34	12.626%	$162.5644	$162.56	$162.55	$162.60
Purchase #2	$125.41	11.761%	$140.1595	$140.16	$140.15	$140.20
Purchase #3	$78.98	12.772%	$89.0673	$89.07	$89.05	$89.10
Purchase #4	$96.92	10.362%	$106.9629	$106.96	$106.95	$107.00
Purchase #5	$148.99	10.381%	$164.4567	$164.46	$164.45	$164.50
Purchase #6	$179.25	7.841%	$193.305	$193.31	$193.30	$193.30
Purchase #7	$142.97	12.603%	$160.9885	$160.99	$161.00	$161.00
7 purchase totals =	$916.86		$1,017.5043	$1,017.51	$1,017.45	$1,017.70