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	$165.86	3.202%	$171.1708	$171.17	$171.15	$171.20
Purchase #2	$225.73	3.331%	$233.2491	$233.25	$233.25	$233.20
Purchase #3	$218.36	8.828%	$237.6368	$237.64	$237.65	$237.60
Purchase #4	$91.96	11.654%	$102.677	$102.68	$102.70	$102.70
Purchase #5	$80.47	12.814%	$90.7814	$90.78	$90.80	$90.80
Purchase #6	$146.36	5.116%	$153.8478	$153.85	$153.85	$153.80
Purchase #7	$31.74	6.264%	$33.7282	$33.73	$33.75	$33.70
7 purchase totals =	$960.48		$1,023.0911	$1,023.10	$1,023.15	$1,023.00