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	$92.32	13.731%	$104.9965	$105.00	$105.00	$105.00
Purchase #2	$59.28	13.133%	$67.0652	$67.07	$67.05	$67.10
Purchase #3	$143.74	5.770%	$152.0338	$152.03	$152.05	$152.00
Purchase #4	$171.64	9.818%	$188.4916	$188.49	$188.50	$188.50
Purchase #5	$40.53	5.182%	$42.6303	$42.63	$42.65	$42.60
Purchase #6	$129.88	5.729%	$137.3208	$137.32	$137.30	$137.30
Purchase #7	$45.42	11.304%	$50.5543	$50.55	$50.55	$50.60
7 purchase totals =	$682.81		$743.0925	$743.09	$743.10	$743.10