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	$83.26	7.176%	$89.2347	$89.23	$89.25	$89.20
Purchase #2	$52.46	12.679%	$59.1114	$59.11	$59.10	$59.10
Purchase #3	$154.46	10.121%	$170.0929	$170.09	$170.10	$170.10
Purchase #4	$210.40	11.818%	$235.2651	$235.27	$235.25	$235.30
Purchase #5	$234.32	6.665%	$249.9374	$249.94	$249.95	$249.90
Purchase #6	$29.99	5.465%	$31.629	$31.63	$31.65	$31.60
Purchase #7	$205.66	10.129%	$226.4913	$226.49	$226.50	$226.50
7 purchase totals =	$970.55		$1,061.7618	$1,061.76	$1,061.80	$1,061.70