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	$148.87	7.864%	$160.5771	$160.58	$160.60	$160.60
Purchase #2	$35.27	6.439%	$37.541	$37.54	$37.55	$37.50
Purchase #3	$35.48	9.621%	$38.8935	$38.89	$38.90	$38.90
Purchase #4	$201.85	3.544%	$209.0036	$209.00	$209.00	$209.00
Purchase #5	$41.34	5.125%	$43.4587	$43.46	$43.45	$43.50
Purchase #6	$224.55	9.304%	$245.4421	$245.44	$245.45	$245.40
Purchase #7	$140.56	12.817%	$158.5756	$158.58	$158.60	$158.60
7 purchase totals =	$827.92		$893.4916	$893.49	$893.55	$893.50