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	$128.51	13.627%	$146.0221	$146.02	$146.00	$146.00
Purchase #2	$187.48	10.722%	$207.5816	$207.58	$207.60	$207.60
Purchase #3	$233.36	9.380%	$255.2492	$255.25	$255.25	$255.20
Purchase #4	$178.65	7.169%	$191.4574	$191.46	$191.45	$191.50
Purchase #5	$200.83	9.352%	$219.6116	$219.61	$219.60	$219.60
Purchase #6	$76.69	6.197%	$81.4425	$81.44	$81.45	$81.40
Purchase #7	$27.76	13.529%	$31.5157	$31.52	$31.50	$31.50
7 purchase totals =	$1,033.28		$1,132.8801	$1,132.88	$1,132.85	$1,132.80