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	$158.60	12.474%	$178.3838	$178.38	$178.40	$178.40
Purchase #2	$140.66	11.556%	$156.9147	$156.91	$156.90	$156.90
Purchase #3	$98.75	4.346%	$103.0417	$103.04	$103.05	$103.00
Purchase #4	$189.57	11.190%	$210.7829	$210.78	$210.80	$210.80
Purchase #5	$106.82	11.141%	$118.7208	$118.72	$118.70	$118.70
Purchase #6	$54.39	10.494%	$60.0977	$60.10	$60.10	$60.10
Purchase #7	$183.54	13.561%	$208.4299	$208.43	$208.45	$208.40
7 purchase totals =	$932.33		$1,036.3715	$1,036.36	$1,036.40	$1,036.30