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	$163.73	4.385%	$170.9096	$170.91	$170.90	$170.90
Purchase #2	$72.29	9.132%	$78.8915	$78.89	$78.90	$78.90
Purchase #3	$57.39	6.287%	$60.9981	$61.00	$61.00	$61.00
Purchase #4	$179.28	3.656%	$185.8345	$185.83	$185.85	$185.80
Purchase #5	$80.37	13.847%	$91.4988	$91.50	$91.50	$91.50
Purchase #6	$112.36	5.752%	$118.8229	$118.82	$118.80	$118.80
Purchase #7	$234.28	10.646%	$259.2214	$259.22	$259.20	$259.20
7 purchase totals =	$899.70		$966.1768	$966.17	$966.15	$966.10