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	$232.80	5.716%	$246.1068	$246.11	$246.10	$246.10
Purchase #2	$13.77	12.791%	$15.5313	$15.53	$15.55	$15.50
Purchase #3	$101.70	7.183%	$109.0051	$109.01	$109.00	$109.00
Purchase #4	$243.57	12.684%	$274.4644	$274.46	$274.45	$274.50
Purchase #5	$214.76	6.834%	$229.4367	$229.44	$229.45	$229.40
Purchase #6	$155.25	4.649%	$162.4676	$162.47	$162.45	$162.50
Purchase #7	$48.67	11.465%	$54.25	$54.25	$54.25	$54.30
7 purchase totals =	$1,010.52		$1,091.2619	$1,091.27	$1,091.25	$1,091.30