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	$156.76	10.289%	$172.889	$172.89	$172.90	$172.90
Purchase #2	$130.60	11.535%	$145.6647	$145.66	$145.65	$145.70
Purchase #3	$162.42	4.522%	$169.7646	$169.76	$169.75	$169.80
Purchase #4	$87.80	6.337%	$93.3639	$93.36	$93.35	$93.40
Purchase #5	$102.93	6.402%	$109.5196	$109.52	$109.50	$109.50
Purchase #6	$229.73	10.554%	$253.9757	$253.98	$254.00	$254.00
Purchase #7	$121.92	11.749%	$136.2444	$136.24	$136.25	$136.20
7 purchase totals =	$992.16		$1,081.4219	$1,081.41	$1,081.40	$1,081.50