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	$85.93	4.462%	$89.7642	$89.76	$89.75	$89.80
Purchase #2	$100.75	5.604%	$106.396	$106.40	$106.40	$106.40
Purchase #3	$103.61	12.865%	$116.9394	$116.94	$116.95	$116.90
Purchase #4	$140.88	12.302%	$158.2111	$158.21	$158.20	$158.20
Purchase #5	$243.61	12.440%	$273.9151	$273.92	$273.90	$273.90
Purchase #6	$156.71	9.821%	$172.1005	$172.10	$172.10	$172.10
Purchase #7	$146.88	7.270%	$157.5582	$157.56	$157.55	$157.60
7 purchase totals =	$978.37		$1,074.8845	$1,074.89	$1,074.85	$1,074.90