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	$133.37	10.626%	$147.5419	$147.54	$147.55	$147.50
Purchase #2	$85.36	4.836%	$89.488	$89.49	$89.50	$89.50
Purchase #3	$54.51	13.711%	$61.9839	$61.98	$62.00	$62.00
Purchase #4	$73.93	10.218%	$81.4842	$81.48	$81.50	$81.50
Purchase #5	$207.30	10.480%	$229.025	$229.03	$229.05	$229.00
Purchase #6	$21.30	13.495%	$24.1744	$24.17	$24.15	$24.20
Purchase #7	$18.35	11.624%	$20.483	$20.48	$20.50	$20.50
7 purchase totals =	$594.12		$654.1804	$654.17	$654.25	$654.20