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	$99.48	10.404%	$109.8299	$109.83	$109.85	$109.80
Purchase #2	$76.92	10.514%	$85.0074	$85.01	$85.00	$85.00
Purchase #3	$140.88	7.691%	$151.7151	$151.72	$151.70	$151.70
Purchase #4	$16.96	6.145%	$18.0022	$18.00	$18.00	$18.00
Purchase #5	$41.38	3.161%	$42.688	$42.69	$42.70	$42.70
Purchase #6	$107.27	10.168%	$118.1772	$118.18	$118.20	$118.20
Purchase #7	$6.28	5.526%	$6.627	$6.63	$6.65	$6.60
7 purchase totals =	$489.17		$532.0468	$532.06	$532.10	$532.00