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	$96.59	13.756%	$109.8769	$109.88	$109.90	$109.90
Purchase #2	$172.76	13.622%	$196.2934	$196.29	$196.30	$196.30
Purchase #3	$179.33	6.470%	$190.9327	$190.93	$190.95	$190.90
Purchase #4	$112.34	4.698%	$117.6177	$117.62	$117.60	$117.60
Purchase #5	$209.81	6.556%	$223.5651	$223.57	$223.55	$223.60
Purchase #6	$76.66	12.306%	$86.0938	$86.09	$86.10	$86.10
Purchase #7	$112.97	11.822%	$126.3253	$126.33	$126.35	$126.30
7 purchase totals =	$960.46		$1,050.7049	$1,050.71	$1,050.75	$1,050.70