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	$125.92	4.306%	$131.3421	$131.34	$131.35	$131.30
Purchase #2	$95.49	4.636%	$99.9169	$99.92	$99.90	$99.90
Purchase #3	$225.52	6.193%	$239.4865	$239.49	$239.50	$239.50
Purchase #4	$128.27	9.346%	$140.2581	$140.26	$140.25	$140.30
Purchase #5	$205.40	5.212%	$216.1054	$216.11	$216.10	$216.10
Purchase #6	$152.75	10.216%	$168.3549	$168.35	$168.35	$168.40
Purchase #7	$70.52	10.598%	$77.9937	$77.99	$78.00	$78.00
7 purchase totals =	$1,003.87		$1,073.4576	$1,073.46	$1,073.45	$1,073.50