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	$35.48	9.196%	$38.7427	$38.74	$38.75	$38.70
Purchase #2	$153.84	12.401%	$172.9177	$172.92	$172.90	$172.90
Purchase #3	$225.46	4.284%	$235.1187	$235.12	$235.10	$235.10
Purchase #4	$85.67	6.676%	$91.3893	$91.39	$91.40	$91.40
Purchase #5	$152.39	9.310%	$166.5775	$166.58	$166.60	$166.60
Purchase #6	$152.41	12.740%	$171.827	$171.83	$171.85	$171.80
Purchase #7	$173.67	13.721%	$197.4993	$197.50	$197.50	$197.50
7 purchase totals =	$978.92		$1,074.0722	$1,074.08	$1,074.10	$1,074.00