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	$46.53	10.552%	$51.4398	$51.44	$51.45	$51.40
Purchase #2	$198.63	13.156%	$224.7618	$224.76	$224.75	$224.80
Purchase #3	$100.43	11.482%	$111.9614	$111.96	$111.95	$112.00
Purchase #4	$102.48	10.360%	$113.0969	$113.10	$113.10	$113.10
Purchase #5	$200.97	10.144%	$221.3564	$221.36	$221.35	$221.40
Purchase #6	$152.83	4.421%	$159.5866	$159.59	$159.60	$159.60
Purchase #7	$236.89	3.596%	$245.4086	$245.41	$245.40	$245.40
7 purchase totals =	$1,038.76		$1,127.6115	$1,127.62	$1,127.60	$1,127.70