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	$166.32	4.837%	$174.3649	$174.36	$174.35	$174.40
Purchase #2	$98.65	4.165%	$102.7588	$102.76	$102.75	$102.80
Purchase #3	$116.54	12.694%	$131.3336	$131.33	$131.35	$131.30
Purchase #4	$147.70	3.355%	$152.6553	$152.66	$152.65	$152.70
Purchase #5	$219.36	10.256%	$241.8576	$241.86	$241.85	$241.90
Purchase #6	$50.53	5.370%	$53.2435	$53.24	$53.25	$53.20
Purchase #7	$100.48	8.782%	$109.3042	$109.30	$109.30	$109.30
7 purchase totals =	$899.58		$965.5179	$965.51	$965.50	$965.60