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	$117.59	8.351%	$127.4099	$127.41	$127.40	$127.40
Purchase #2	$100.66	4.201%	$104.8887	$104.89	$104.90	$104.90
Purchase #3	$242.31	3.812%	$251.5469	$251.55	$251.55	$251.50
Purchase #4	$30.49	4.289%	$31.7977	$31.80	$31.80	$31.80
Purchase #5	$131.38	11.537%	$146.5373	$146.54	$146.55	$146.50
Purchase #6	$114.73	8.795%	$124.8205	$124.82	$124.80	$124.80
Purchase #7	$104.60	5.317%	$110.1616	$110.16	$110.15	$110.20
7 purchase totals =	$841.76		$897.1626	$897.17	$897.15	$897.10