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	$173.43	5.134%	$182.3339	$182.33	$182.35	$182.30
Purchase #2	$235.48	3.776%	$244.3717	$244.37	$244.35	$244.40
Purchase #3	$111.72	10.393%	$123.3311	$123.33	$123.35	$123.30
Purchase #4	$79.99	7.419%	$85.9245	$85.92	$85.90	$85.90
Purchase #5	$134.89	8.471%	$146.3165	$146.32	$146.30	$146.30
Purchase #6	$78.36	10.486%	$86.5768	$86.58	$86.60	$86.60
Purchase #7	$181.52	4.815%	$190.2602	$190.26	$190.25	$190.30
7 purchase totals =	$995.39		$1,059.1147	$1,059.11	$1,059.10	$1,059.10