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	$59.50	10.337%	$65.6505	$65.65	$65.65	$65.70
Purchase #2	$58.75	10.331%	$64.8195	$64.82	$64.80	$64.80
Purchase #3	$148.85	13.778%	$169.3586	$169.36	$169.35	$169.40
Purchase #4	$29.71	12.663%	$33.4722	$33.47	$33.45	$33.50
Purchase #5	$239.97	6.216%	$254.8865	$254.89	$254.90	$254.90
Purchase #6	$18.69	8.749%	$20.3252	$20.33	$20.35	$20.30
Purchase #7	$106.25	3.175%	$109.6234	$109.62	$109.60	$109.60
7 purchase totals =	$661.72		$718.1359	$718.14	$718.10	$718.20