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	$66.62	11.289%	$74.1407	$74.14	$74.15	$74.10
Purchase #2	$96.48	10.619%	$106.7252	$106.73	$106.75	$106.70
Purchase #3	$118.47	11.362%	$131.9306	$131.93	$131.95	$131.90
Purchase #4	$150.41	4.268%	$156.8295	$156.83	$156.85	$156.80
Purchase #5	$127.61	3.368%	$131.9079	$131.91	$131.90	$131.90
Purchase #6	$200.74	12.196%	$225.2223	$225.22	$225.20	$225.20
Purchase #7	$38.71	9.331%	$42.322	$42.32	$42.30	$42.30
7 purchase totals =	$799.04		$869.0782	$869.08	$869.10	$868.90