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	$237.57	7.402%	$255.1549	$255.15	$255.15	$255.20
Purchase #2	$82.61	9.146%	$90.1655	$90.17	$90.15	$90.20
Purchase #3	$167.96	3.141%	$173.2356	$173.24	$173.25	$173.20
Purchase #4	$150.83	5.331%	$158.8707	$158.87	$158.85	$158.90
Purchase #5	$195.90	3.798%	$203.3403	$203.34	$203.35	$203.30
Purchase #6	$192.88	3.639%	$199.8989	$199.90	$199.90	$199.90
Purchase #7	$103.77	5.685%	$109.6693	$109.67	$109.65	$109.70
7 purchase totals =	$1,131.52		$1,190.3352	$1,190.34	$1,190.30	$1,190.40