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	$46.49	10.842%	$51.5304	$51.53	$51.55	$51.50
Purchase #2	$73.72	11.803%	$82.4212	$82.42	$82.40	$82.40
Purchase #3	$43.88	6.651%	$46.7985	$46.80	$46.80	$46.80
Purchase #4	$9.50	10.530%	$10.5004	$10.50	$10.50	$10.50
Purchase #5	$105.56	8.479%	$114.5104	$114.51	$114.50	$114.50
Purchase #6	$112.69	13.103%	$127.4558	$127.46	$127.45	$127.50
Purchase #7	$209.78	6.805%	$224.0555	$224.06	$224.05	$224.10
7 purchase totals =	$601.62		$657.2722	$657.28	$657.25	$657.30