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	$83.53	9.138%	$91.163	$91.16	$91.15	$91.20
Purchase #2	$85.34	13.417%	$96.7901	$96.79	$96.80	$96.80
Purchase #3	$51.44	11.150%	$57.1756	$57.18	$57.20	$57.20
Purchase #4	$93.98	8.687%	$102.144	$102.14	$102.15	$102.10
Purchase #5	$92.34	13.864%	$105.142	$105.14	$105.15	$105.10
Purchase #6	$79.97	11.503%	$89.1689	$89.17	$89.15	$89.20
Purchase #7	$234.66	8.666%	$254.9956	$255.00	$255.00	$255.00
7 purchase totals =	$721.26		$796.5792	$796.58	$796.60	$796.60