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	$165.43	13.557%	$187.8573	$187.86	$187.85	$187.90
Purchase #2	$229.92	10.469%	$253.9903	$253.99	$254.00	$254.00
Purchase #3	$34.83	8.736%	$37.8727	$37.87	$37.85	$37.90
Purchase #4	$123.91	3.522%	$128.2741	$128.27	$128.25	$128.30
Purchase #5	$155.82	4.289%	$162.5031	$162.50	$162.50	$162.50
Purchase #6	$30.71	5.822%	$32.4979	$32.50	$32.50	$32.50
Purchase #7	$122.29	5.828%	$129.4171	$129.42	$129.40	$129.40
7 purchase totals =	$862.91		$932.4125	$932.41	$932.35	$932.50