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	$57.73	6.228%	$61.3254	$61.33	$61.35	$61.30
Purchase #2	$56.51	4.541%	$59.0761	$59.08	$59.10	$59.10
Purchase #3	$121.92	11.804%	$136.3114	$136.31	$136.30	$136.30
Purchase #4	$175.84	5.109%	$184.8237	$184.82	$184.80	$184.80
Purchase #5	$186.91	7.198%	$200.3638	$200.36	$200.35	$200.40
Purchase #6	$47.96	8.376%	$51.9771	$51.98	$52.00	$52.00
Purchase #7	$119.98	9.638%	$131.5437	$131.54	$131.55	$131.50
7 purchase totals =	$766.85		$825.4212	$825.42	$825.45	$825.40