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	$154.65	10.663%	$171.1403	$171.14	$171.15	$171.10
Purchase #2	$50.97	11.351%	$56.7556	$56.76	$56.75	$56.80
Purchase #3	$203.90	9.177%	$222.6119	$222.61	$222.60	$222.60
Purchase #4	$160.38	7.765%	$172.8335	$172.83	$172.85	$172.80
Purchase #5	$173.75	13.313%	$196.8813	$196.88	$196.90	$196.90
Purchase #6	$7.85	5.383%	$8.2726	$8.27	$8.25	$8.30
Purchase #7	$188.76	5.273%	$198.7133	$198.71	$198.70	$198.70
7 purchase totals =	$940.26		$1,027.2085	$1,027.20	$1,027.20	$1,027.20