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	$164.31	4.701%	$172.0342	$172.03	$172.05	$172.00
Purchase #2	$53.94	3.564%	$55.8624	$55.86	$55.85	$55.90
Purchase #3	$115.59	12.429%	$129.9567	$129.96	$129.95	$130.00
Purchase #4	$156.86	7.700%	$168.9382	$168.94	$168.95	$168.90
Purchase #5	$83.54	8.520%	$90.6576	$90.66	$90.65	$90.70
Purchase #6	$239.31	8.483%	$259.6107	$259.61	$259.60	$259.60
Purchase #7	$178.86	5.272%	$188.2895	$188.29	$188.30	$188.30
7 purchase totals =	$992.41		$1,065.3493	$1,065.35	$1,065.35	$1,065.40