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	$170.86	11.417%	$190.3671	$190.37	$190.35	$190.40
Purchase #2	$211.64	5.786%	$223.8855	$223.89	$223.90	$223.90
Purchase #3	$50.64	5.822%	$53.5883	$53.59	$53.60	$53.60
Purchase #4	$29.43	9.356%	$32.1835	$32.18	$32.20	$32.20
Purchase #5	$41.46	7.245%	$44.4638	$44.46	$44.45	$44.50
Purchase #6	$29.27	7.188%	$31.3739	$31.37	$31.35	$31.40
Purchase #7	$175.82	4.760%	$184.189	$184.19	$184.20	$184.20
7 purchase totals =	$709.12		$760.0511	$760.05	$760.05	$760.20