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	$246.71	10.849%	$273.4756	$273.48	$273.50	$273.50
Purchase #2	$225.58	11.416%	$251.3322	$251.33	$251.35	$251.30
Purchase #3	$53.93	5.458%	$56.8735	$56.87	$56.85	$56.90
Purchase #4	$82.46	13.266%	$93.3991	$93.40	$93.40	$93.40
Purchase #5	$30.66	4.501%	$32.04	$32.04	$32.05	$32.00
Purchase #6	$149.75	4.749%	$156.8616	$156.86	$156.85	$156.90
Purchase #7	$245.32	13.274%	$277.8838	$277.88	$277.90	$277.90
7 purchase totals =	$1,034.41		$1,141.8658	$1,141.86	$1,141.90	$1,141.90