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	$43.58	6.367%	$46.3547	$46.35	$46.35	$46.40
Purchase #2	$182.86	12.284%	$205.3225	$205.32	$205.30	$205.30
Purchase #3	$159.69	6.166%	$169.5365	$169.54	$169.55	$169.50
Purchase #4	$226.82	12.452%	$255.0636	$255.06	$255.05	$255.10
Purchase #5	$145.74	4.146%	$151.7824	$151.78	$151.80	$151.80
Purchase #6	$146.44	11.673%	$163.5339	$163.53	$163.55	$163.50
Purchase #7	$206.35	8.514%	$223.9186	$223.92	$223.90	$223.90
7 purchase totals =	$1,111.48		$1,215.5122	$1,215.50	$1,215.50	$1,215.50