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	$161.84	6.363%	$172.1379	$172.14	$172.15	$172.10
Purchase #2	$246.33	11.112%	$273.7022	$273.70	$273.70	$273.70
Purchase #3	$24.88	3.203%	$25.6769	$25.68	$25.70	$25.70
Purchase #4	$71.44	10.310%	$78.8055	$78.81	$78.80	$78.80
Purchase #5	$21.61	13.713%	$24.5734	$24.57	$24.55	$24.60
Purchase #6	$111.98	10.190%	$123.3908	$123.39	$123.40	$123.40
Purchase #7	$67.92	7.107%	$72.7471	$72.75	$72.75	$72.70
7 purchase totals =	$706.00		$771.0338	$771.04	$771.05	$771.00