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	$242.78	8.130%	$262.518	$262.52	$262.50	$262.50
Purchase #2	$96.89	13.110%	$109.5923	$109.59	$109.60	$109.60
Purchase #3	$196.89	8.818%	$214.2518	$214.25	$214.25	$214.30
Purchase #4	$205.63	4.557%	$215.0006	$215.00	$215.00	$215.00
Purchase #5	$68.28	4.559%	$71.3929	$71.39	$71.40	$71.40
Purchase #6	$84.89	9.819%	$93.2253	$93.23	$93.25	$93.20
Purchase #7	$27.98	9.414%	$30.614	$30.61	$30.60	$30.60
7 purchase totals =	$923.34		$996.5949	$996.59	$996.60	$996.60