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	$52.94	4.423%	$55.2815	$55.28	$55.30	$55.30
Purchase #2	$187.30	10.397%	$206.7736	$206.77	$206.75	$206.80
Purchase #3	$59.93	7.659%	$64.52	$64.52	$64.50	$64.50
Purchase #4	$206.53	10.840%	$228.9179	$228.92	$228.90	$228.90
Purchase #5	$238.72	13.374%	$270.6464	$270.65	$270.65	$270.60
Purchase #6	$87.54	8.790%	$95.2348	$95.23	$95.25	$95.20
Purchase #7	$127.69	9.748%	$140.1372	$140.14	$140.15	$140.10
7 purchase totals =	$960.65		$1,061.5114	$1,061.51	$1,061.50	$1,061.40