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	$118.50	12.569%	$133.3943	$133.39	$133.40	$133.40
Purchase #2	$164.57	10.512%	$181.8696	$181.87	$181.85	$181.90
Purchase #3	$128.56	10.749%	$142.3789	$142.38	$142.40	$142.40
Purchase #4	$39.29	11.560%	$43.8319	$43.83	$43.85	$43.80
Purchase #5	$250.71	13.204%	$283.8137	$283.81	$283.80	$283.80
Purchase #6	$58.41	13.355%	$66.2107	$66.21	$66.20	$66.20
Purchase #7	$96.52	13.866%	$109.9035	$109.90	$109.90	$109.90
7 purchase totals =	$856.56		$961.4026	$961.39	$961.40	$961.40