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	$59.58	6.378%	$63.38	$63.38	$63.40	$63.40
Purchase #2	$180.35	5.349%	$189.9969	$190.00	$190.00	$190.00
Purchase #3	$36.69	11.183%	$40.793	$40.79	$40.80	$40.80
Purchase #4	$17.62	6.240%	$18.7195	$18.72	$18.70	$18.70
Purchase #5	$142.57	5.796%	$150.8334	$150.83	$150.85	$150.80
Purchase #6	$170.56	8.869%	$185.687	$185.69	$185.70	$185.70
Purchase #7	$51.39	12.778%	$57.9566	$57.96	$57.95	$58.00
7 purchase totals =	$658.76		$707.3664	$707.37	$707.40	$707.40