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	$198.58	8.781%	$216.0173	$216.02	$216.00	$216.00
Purchase #2	$245.40	11.588%	$273.837	$273.84	$273.85	$273.80
Purchase #3	$37.93	11.729%	$42.3788	$42.38	$42.40	$42.40
Purchase #4	$45.76	13.369%	$51.8777	$51.88	$51.90	$51.90
Purchase #5	$179.85	6.697%	$191.8946	$191.89	$191.90	$191.90
Purchase #6	$201.43	10.487%	$222.554	$222.55	$222.55	$222.60
Purchase #7	$109.99	12.119%	$123.3197	$123.32	$123.30	$123.30
7 purchase totals =	$1,018.94		$1,121.8791	$1,121.88	$1,121.90	$1,121.90