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	$189.71	10.822%	$210.2404	$210.24	$210.25	$210.20
Purchase #2	$61.71	12.865%	$69.649	$69.65	$69.65	$69.60
Purchase #3	$34.61	9.543%	$37.9128	$37.91	$37.90	$37.90
Purchase #4	$10.32	5.482%	$10.8857	$10.89	$10.90	$10.90
Purchase #5	$66.73	8.702%	$72.5368	$72.54	$72.55	$72.50
Purchase #6	$100.98	9.365%	$110.4368	$110.44	$110.45	$110.40
Purchase #7	$244.36	11.554%	$272.5934	$272.59	$272.60	$272.60
7 purchase totals =	$708.42		$784.2549	$784.26	$784.30	$784.10