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	$233.45	5.147%	$245.4657	$245.47	$245.45	$245.50
Purchase #2	$30.53	7.596%	$32.8491	$32.85	$32.85	$32.80
Purchase #3	$88.98	13.395%	$100.8989	$100.90	$100.90	$100.90
Purchase #4	$11.59	11.565%	$12.9304	$12.93	$12.95	$12.90
Purchase #5	$149.29	8.700%	$162.2782	$162.28	$162.30	$162.30
Purchase #6	$75.38	9.224%	$82.3331	$82.33	$82.35	$82.30
Purchase #7	$144.30	3.283%	$149.0374	$149.04	$149.05	$149.00
7 purchase totals =	$733.52		$785.7928	$785.80	$785.85	$785.70