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	$91.25	5.703%	$96.454	$96.45	$96.45	$96.50
Purchase #2	$16.58	10.513%	$18.3231	$18.32	$18.30	$18.30
Purchase #3	$127.35	6.857%	$136.0824	$136.08	$136.10	$136.10
Purchase #4	$11.97	12.486%	$13.4646	$13.46	$13.45	$13.50
Purchase #5	$61.84	6.323%	$65.7501	$65.75	$65.75	$65.80
Purchase #6	$72.55	13.861%	$82.6062	$82.61	$82.60	$82.60
Purchase #7	$216.72	12.695%	$244.2326	$244.23	$244.25	$244.20
7 purchase totals =	$598.26		$656.9130	$656.90	$656.90	$657.00