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	$140.59	3.661%	$145.737	$145.74	$145.75	$145.70
Purchase #2	$140.40	9.772%	$154.1199	$154.12	$154.10	$154.10
Purchase #3	$51.39	13.352%	$58.2516	$58.25	$58.25	$58.30
Purchase #4	$166.53	12.386%	$187.1564	$187.16	$187.15	$187.20
Purchase #5	$55.41	11.189%	$61.6098	$61.61	$61.60	$61.60
Purchase #6	$41.50	3.818%	$43.0845	$43.08	$43.10	$43.10
Purchase #7	$98.50	12.201%	$110.518	$110.52	$110.50	$110.50
7 purchase totals =	$694.32		$760.4772	$760.48	$760.45	$760.50