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	$210.49	5.503%	$222.0733	$222.07	$222.05	$222.10
Purchase #2	$128.26	12.299%	$144.0347	$144.03	$144.05	$144.00
Purchase #3	$170.89	7.710%	$184.0656	$184.07	$184.05	$184.10
Purchase #4	$190.53	10.389%	$210.3242	$210.32	$210.30	$210.30
Purchase #5	$91.81	9.221%	$100.2758	$100.28	$100.30	$100.30
Purchase #6	$106.46	9.458%	$116.529	$116.53	$116.55	$116.50
Purchase #7	$142.63	6.489%	$151.8853	$151.89	$151.90	$151.90
7 purchase totals =	$1,041.07		$1,129.1879	$1,129.19	$1,129.20	$1,129.20