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	$234.71	3.304%	$242.4648	$242.46	$242.45	$242.50
Purchase #2	$160.36	5.232%	$168.75	$168.75	$168.75	$168.80
Purchase #3	$173.85	13.115%	$196.6504	$196.65	$196.65	$196.70
Purchase #4	$167.36	11.489%	$186.588	$186.59	$186.60	$186.60
Purchase #5	$66.38	8.253%	$71.8583	$71.86	$71.85	$71.90
Purchase #6	$111.31	13.335%	$126.1532	$126.15	$126.15	$126.20
Purchase #7	$62.48	11.805%	$69.8558	$69.86	$69.85	$69.90
7 purchase totals =	$976.45		$1,062.3205	$1,062.32	$1,062.30	$1,062.60