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	$137.88	8.828%	$150.052	$150.05	$150.05	$150.10
Purchase #2	$92.69	7.442%	$99.588	$99.59	$99.60	$99.60
Purchase #3	$58.55	12.141%	$65.6586	$65.66	$65.65	$65.70
Purchase #4	$57.85	3.218%	$59.7116	$59.71	$59.70	$59.70
Purchase #5	$76.75	8.254%	$83.0849	$83.08	$83.10	$83.10
Purchase #6	$46.74	8.719%	$50.8153	$50.82	$50.80	$50.80
Purchase #7	$227.36	5.830%	$240.6151	$240.62	$240.60	$240.60
7 purchase totals =	$697.82		$749.5255	$749.53	$749.50	$749.60