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	$98.81	13.872%	$112.5169	$112.52	$112.50	$112.50
Purchase #2	$137.47	4.398%	$143.5159	$143.52	$143.50	$143.50
Purchase #3	$212.93	4.376%	$222.2478	$222.25	$222.25	$222.20
Purchase #4	$247.53	6.773%	$264.2952	$264.30	$264.30	$264.30
Purchase #5	$70.54	4.241%	$73.5316	$73.53	$73.55	$73.50
Purchase #6	$39.26	7.651%	$42.2638	$42.26	$42.25	$42.30
Purchase #7	$98.71	11.366%	$109.9294	$109.93	$109.95	$109.90
7 purchase totals =	$905.25		$968.3006	$968.31	$968.30	$968.20