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	$161.89	5.787%	$171.2586	$171.26	$171.25	$171.30
Purchase #2	$32.28	4.650%	$33.781	$33.78	$33.80	$33.80
Purchase #3	$81.60	13.822%	$92.8788	$92.88	$92.90	$92.90
Purchase #4	$216.66	5.635%	$228.8688	$228.87	$228.85	$228.90
Purchase #5	$245.36	8.147%	$265.3495	$265.35	$265.35	$265.30
Purchase #6	$237.84	12.835%	$268.3668	$268.37	$268.35	$268.40
Purchase #7	$18.59	11.189%	$20.67	$20.67	$20.65	$20.70
7 purchase totals =	$994.22		$1,081.1735	$1,081.18	$1,081.15	$1,081.30