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	$170.39	5.489%	$179.7427	$179.74	$179.75	$179.70
Purchase #2	$142.60	4.153%	$148.5222	$148.52	$148.50	$148.50
Purchase #3	$137.60	13.573%	$156.2764	$156.28	$156.30	$156.30
Purchase #4	$179.38	9.393%	$196.2292	$196.23	$196.25	$196.20
Purchase #5	$206.59	12.866%	$233.1699	$233.17	$233.15	$233.20
Purchase #6	$208.89	11.283%	$232.4591	$232.46	$232.45	$232.50
Purchase #7	$117.94	4.505%	$123.2532	$123.25	$123.25	$123.30
7 purchase totals =	$1,163.39		$1,269.6527	$1,269.65	$1,269.65	$1,269.70