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	$73.36	8.829%	$79.837	$79.84	$79.85	$79.80
Purchase #2	$91.29	10.589%	$100.9567	$100.96	$100.95	$101.00
Purchase #3	$174.52	5.639%	$184.3612	$184.36	$184.35	$184.40
Purchase #4	$200.55	4.682%	$209.9398	$209.94	$209.95	$209.90
Purchase #5	$111.93	4.290%	$116.7318	$116.73	$116.75	$116.70
Purchase #6	$200.49	11.607%	$223.7609	$223.76	$223.75	$223.80
Purchase #7	$169.60	3.709%	$175.8905	$175.89	$175.90	$175.90
7 purchase totals =	$1,021.74		$1,091.4779	$1,091.48	$1,091.50	$1,091.50