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	$100.54	9.285%	$109.8751	$109.88	$109.90	$109.90
Purchase #2	$15.58	12.789%	$17.5725	$17.57	$17.55	$17.60
Purchase #3	$183.46	11.591%	$204.7248	$204.72	$204.70	$204.70
Purchase #4	$164.70	12.361%	$185.0586	$185.06	$185.05	$185.10
Purchase #5	$69.43	10.243%	$76.5417	$76.54	$76.55	$76.50
Purchase #6	$185.99	6.552%	$198.1761	$198.18	$198.20	$198.20
Purchase #7	$216.41	4.230%	$225.5641	$225.56	$225.55	$225.60
7 purchase totals =	$936.11		$1,017.5129	$1,017.51	$1,017.50	$1,017.60