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	$104.92	4.253%	$109.3822	$109.38	$109.40	$109.40
Purchase #2	$19.52	5.103%	$20.5161	$20.52	$20.50	$20.50
Purchase #3	$155.45	7.609%	$167.2782	$167.28	$167.30	$167.30
Purchase #4	$77.90	12.364%	$87.5316	$87.53	$87.55	$87.50
Purchase #5	$109.74	12.743%	$123.7242	$123.72	$123.70	$123.70
Purchase #6	$120.47	13.315%	$136.5106	$136.51	$136.50	$136.50
Purchase #7	$101.26	12.639%	$114.0583	$114.06	$114.05	$114.10
7 purchase totals =	$689.26		$759.0012	$759.00	$759.00	$759.00