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	$162.74	11.268%	$181.0775	$181.08	$181.10	$181.10
Purchase #2	$16.94	3.203%	$17.4826	$17.48	$17.50	$17.50
Purchase #3	$91.91	13.312%	$104.1451	$104.15	$104.15	$104.10
Purchase #4	$79.66	12.121%	$89.3156	$89.32	$89.30	$89.30
Purchase #5	$223.72	12.325%	$251.2935	$251.29	$251.30	$251.30
Purchase #6	$59.95	9.429%	$65.6027	$65.60	$65.60	$65.60
Purchase #7	$128.50	10.628%	$142.157	$142.16	$142.15	$142.20
7 purchase totals =	$763.42		$851.0740	$851.08	$851.10	$851.10