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	$23.97	4.781%	$25.116	$25.12	$25.10	$25.10
Purchase #2	$219.77	9.803%	$241.3141	$241.31	$241.30	$241.30
Purchase #3	$89.65	6.501%	$95.4781	$95.48	$95.50	$95.50
Purchase #4	$89.78	7.211%	$96.254	$96.25	$96.25	$96.30
Purchase #5	$159.45	5.734%	$168.5929	$168.59	$168.60	$168.60
Purchase #6	$163.30	4.862%	$171.2396	$171.24	$171.25	$171.20
Purchase #7	$131.75	11.426%	$146.8038	$146.80	$146.80	$146.80
7 purchase totals =	$877.67		$944.7985	$944.79	$944.80	$944.80