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	$73.66	4.106%	$76.6845	$76.68	$76.70	$76.70
Purchase #2	$133.89	13.664%	$152.1847	$152.18	$152.20	$152.20
Purchase #3	$46.39	11.415%	$51.6854	$51.69	$51.70	$51.70
Purchase #4	$124.58	11.823%	$139.3091	$139.31	$139.30	$139.30
Purchase #5	$238.88	10.284%	$263.4464	$263.45	$263.45	$263.40
Purchase #6	$128.38	9.307%	$140.3283	$140.33	$140.35	$140.30
Purchase #7	$176.55	9.216%	$192.8208	$192.82	$192.80	$192.80
7 purchase totals =	$922.33		$1,016.4592	$1,016.46	$1,016.50	$1,016.40