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	$85.52	12.428%	$96.1484	$96.15	$96.15	$96.10
Purchase #2	$233.64	3.701%	$242.287	$242.29	$242.30	$242.30
Purchase #3	$80.41	6.237%	$85.4252	$85.43	$85.45	$85.40
Purchase #4	$64.52	7.872%	$69.599	$69.60	$69.60	$69.60
Purchase #5	$128.76	11.221%	$143.2082	$143.21	$143.20	$143.20
Purchase #6	$79.29	11.440%	$88.3608	$88.36	$88.35	$88.40
Purchase #7	$190.58	13.809%	$216.8972	$216.90	$216.90	$216.90
7 purchase totals =	$862.72		$941.9258	$941.94	$941.95	$941.90