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	$83.85	4.235%	$87.401	$87.40	$87.40	$87.40
Purchase #2	$49.64	5.327%	$52.2843	$52.28	$52.30	$52.30
Purchase #3	$196.63	4.592%	$205.6592	$205.66	$205.65	$205.70
Purchase #4	$37.83	13.225%	$42.833	$42.83	$42.85	$42.80
Purchase #5	$195.94	9.362%	$214.2839	$214.28	$214.30	$214.30
Purchase #6	$177.83	7.207%	$190.6462	$190.65	$190.65	$190.60
Purchase #7	$188.83	11.298%	$210.164	$210.16	$210.15	$210.20
7 purchase totals =	$930.55		$1,003.2716	$1,003.26	$1,003.30	$1,003.30