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	$183.86	9.787%	$201.8544	$201.85	$201.85	$201.90
Purchase #2	$27.86	6.191%	$29.5848	$29.58	$29.60	$29.60
Purchase #3	$141.70	3.209%	$146.2472	$146.25	$146.25	$146.20
Purchase #4	$156.93	4.740%	$164.3685	$164.37	$164.35	$164.40
Purchase #5	$75.83	9.873%	$83.3167	$83.32	$83.30	$83.30
Purchase #6	$92.41	8.645%	$100.3988	$100.40	$100.40	$100.40
Purchase #7	$93.85	6.684%	$100.1229	$100.12	$100.10	$100.10
7 purchase totals =	$772.44		$825.8933	$825.89	$825.85	$825.90