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	$118.90	3.598%	$123.178	$123.18	$123.20	$123.20
Purchase #2	$79.33	7.169%	$85.0172	$85.02	$85.00	$85.00
Purchase #3	$190.59	11.507%	$212.5212	$212.52	$212.50	$212.50
Purchase #4	$179.96	11.389%	$200.4556	$200.46	$200.45	$200.50
Purchase #5	$108.36	5.222%	$114.0186	$114.02	$114.00	$114.00
Purchase #6	$241.87	11.400%	$269.4432	$269.44	$269.45	$269.40
Purchase #7	$69.89	4.782%	$73.2321	$73.23	$73.25	$73.20
7 purchase totals =	$988.90		$1,077.8659	$1,077.87	$1,077.85	$1,077.80