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	$156.69	12.194%	$175.7968	$175.80	$175.80	$175.80
Purchase #2	$106.29	13.147%	$120.2639	$120.26	$120.25	$120.30
Purchase #3	$102.43	11.140%	$113.8407	$113.84	$113.85	$113.80
Purchase #4	$148.59	3.516%	$153.8144	$153.81	$153.80	$153.80
Purchase #5	$152.66	11.666%	$170.4693	$170.47	$170.45	$170.50
Purchase #6	$226.32	3.165%	$233.483	$233.48	$233.50	$233.50
Purchase #7	$33.35	4.614%	$34.8888	$34.89	$34.90	$34.90
7 purchase totals =	$926.33		$1,002.5569	$1,002.55	$1,002.55	$1,002.60