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	$51.90	13.830%	$59.0778	$59.08	$59.10	$59.10
Purchase #2	$61.32	10.771%	$67.9248	$67.92	$67.90	$67.90
Purchase #3	$76.71	9.792%	$84.2214	$84.22	$84.20	$84.20
Purchase #4	$146.64	9.424%	$160.4594	$160.46	$160.45	$160.50
Purchase #5	$161.48	4.484%	$168.7208	$168.72	$168.70	$168.70
Purchase #6	$231.68	10.695%	$256.4582	$256.46	$256.45	$256.50
Purchase #7	$95.62	4.192%	$99.6284	$99.63	$99.65	$99.60
7 purchase totals =	$825.35		$896.4908	$896.49	$896.45	$896.50