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	$100.48	9.151%	$109.6749	$109.67	$109.65	$109.70
Purchase #2	$144.31	8.445%	$156.497	$156.50	$156.50	$156.50
Purchase #3	$242.73	12.515%	$273.1077	$273.11	$273.10	$273.10
Purchase #4	$161.73	4.717%	$169.3588	$169.36	$169.35	$169.40
Purchase #5	$80.60	11.818%	$90.1253	$90.13	$90.15	$90.10
Purchase #6	$219.28	5.180%	$230.6387	$230.64	$230.65	$230.60
Purchase #7	$183.70	5.845%	$194.4373	$194.44	$194.45	$194.40
7 purchase totals =	$1,132.83		$1,223.8397	$1,223.85	$1,223.85	$1,223.80