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	$122.27	4.241%	$127.4555	$127.46	$127.45	$127.50
Purchase #2	$67.96	6.821%	$72.5956	$72.60	$72.60	$72.60
Purchase #3	$248.98	9.121%	$271.6895	$271.69	$271.70	$271.70
Purchase #4	$83.50	10.415%	$92.1965	$92.20	$92.20	$92.20
Purchase #5	$186.27	4.533%	$194.7136	$194.71	$194.70	$194.70
Purchase #6	$16.97	5.852%	$17.9631	$17.96	$17.95	$18.00
Purchase #7	$45.40	3.207%	$46.856	$46.86	$46.85	$46.90
7 purchase totals =	$771.35		$823.4698	$823.48	$823.45	$823.60