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	$159.70	5.372%	$168.2791	$168.28	$168.30	$168.30
Purchase #2	$114.28	13.397%	$129.5901	$129.59	$129.60	$129.60
Purchase #3	$224.33	13.801%	$255.2898	$255.29	$255.30	$255.30
Purchase #4	$150.81	13.279%	$170.8361	$170.84	$170.85	$170.80
Purchase #5	$210.28	5.657%	$222.1755	$222.18	$222.20	$222.20
Purchase #6	$23.32	12.686%	$26.2784	$26.28	$26.30	$26.30
Purchase #7	$220.50	3.328%	$227.8382	$227.84	$227.85	$227.80
7 purchase totals =	$1,103.22		$1,200.2872	$1,200.30	$1,200.40	$1,200.30