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	$196.69	3.718%	$204.0029	$204.00	$204.00	$204.00
Purchase #2	$110.73	6.659%	$118.1035	$118.10	$118.10	$118.10
Purchase #3	$96.49	5.817%	$102.1028	$102.10	$102.10	$102.10
Purchase #4	$135.89	11.477%	$151.4861	$151.49	$151.50	$151.50
Purchase #5	$102.93	6.230%	$109.3425	$109.34	$109.35	$109.30
Purchase #6	$110.26	11.819%	$123.2916	$123.29	$123.30	$123.30
Purchase #7	$55.34	8.212%	$59.8845	$59.88	$59.90	$59.90
7 purchase totals =	$808.33		$868.2139	$868.20	$868.25	$868.20