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	$96.71	11.139%	$107.4825	$107.48	$107.50	$107.50
Purchase #2	$234.60	4.168%	$244.3781	$244.38	$244.40	$244.40
Purchase #3	$19.47	9.393%	$21.2988	$21.30	$21.30	$21.30
Purchase #4	$196.42	4.797%	$205.8423	$205.84	$205.85	$205.80
Purchase #5	$113.29	8.846%	$123.3116	$123.31	$123.30	$123.30
Purchase #6	$7.56	4.568%	$7.9053	$7.91	$7.90	$7.90
Purchase #7	$69.44	6.723%	$74.1085	$74.11	$74.10	$74.10
7 purchase totals =	$737.49		$784.3271	$784.33	$784.35	$784.30