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	$44.55	4.266%	$46.4505	$46.45	$46.45	$46.50
Purchase #2	$67.97	8.766%	$73.9283	$73.93	$73.95	$73.90
Purchase #3	$193.34	13.741%	$219.9068	$219.91	$219.90	$219.90
Purchase #4	$225.30	10.197%	$248.2738	$248.27	$248.25	$248.30
Purchase #5	$72.26	8.727%	$78.5661	$78.57	$78.55	$78.60
Purchase #6	$89.55	6.754%	$95.5982	$95.60	$95.60	$95.60
Purchase #7	$218.90	9.668%	$240.0633	$240.06	$240.05	$240.10
7 purchase totals =	$911.87		$1,002.7870	$1,002.79	$1,002.75	$1,002.90