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	$90.74	6.333%	$96.4866	$96.49	$96.50	$96.50
Purchase #2	$143.64	13.385%	$162.8662	$162.87	$162.85	$162.90
Purchase #3	$146.57	7.502%	$157.5657	$157.57	$157.55	$157.60
Purchase #4	$63.87	3.565%	$66.147	$66.15	$66.15	$66.10
Purchase #5	$86.42	7.197%	$92.6396	$92.64	$92.65	$92.60
Purchase #6	$245.73	7.298%	$263.6634	$263.66	$263.65	$263.70
Purchase #7	$53.92	11.151%	$59.9326	$59.93	$59.95	$59.90
7 purchase totals =	$830.89		$899.3011	$899.31	$899.30	$899.30