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	$49.48	7.488%	$53.1851	$53.19	$53.20	$53.20
Purchase #2	$87.31	10.378%	$96.371	$96.37	$96.35	$96.40
Purchase #3	$200.69	13.211%	$227.2032	$227.20	$227.20	$227.20
Purchase #4	$117.68	4.423%	$122.885	$122.89	$122.90	$122.90
Purchase #5	$118.60	11.232%	$131.9212	$131.92	$131.90	$131.90
Purchase #6	$52.47	13.621%	$59.6169	$59.62	$59.60	$59.60
Purchase #7	$86.94	7.144%	$93.151	$93.15	$93.15	$93.20
7 purchase totals =	$713.17		$784.3334	$784.34	$784.30	$784.40