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	$65.44	5.681%	$69.1576	$69.16	$69.15	$69.20
Purchase #2	$247.91	7.669%	$266.9222	$266.92	$266.90	$266.90
Purchase #3	$81.33	11.657%	$90.8106	$90.81	$90.80	$90.80
Purchase #4	$119.56	6.649%	$127.5095	$127.51	$127.50	$127.50
Purchase #5	$123.71	10.189%	$136.3148	$136.31	$136.30	$136.30
Purchase #6	$83.55	4.617%	$87.4075	$87.41	$87.40	$87.40
Purchase #7	$223.88	4.183%	$233.2449	$233.24	$233.25	$233.20
7 purchase totals =	$945.38		$1,011.3671	$1,011.36	$1,011.30	$1,011.30