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	$108.27	5.187%	$113.886	$113.89	$113.90	$113.90
Purchase #2	$90.40	10.346%	$99.7528	$99.75	$99.75	$99.80
Purchase #3	$133.71	10.533%	$147.7937	$147.79	$147.80	$147.80
Purchase #4	$97.77	10.201%	$107.7435	$107.74	$107.75	$107.70
Purchase #5	$36.77	5.817%	$38.9089	$38.91	$38.90	$38.90
Purchase #6	$64.93	3.196%	$67.0052	$67.01	$67.00	$67.00
Purchase #7	$163.56	13.324%	$185.3527	$185.35	$185.35	$185.40
7 purchase totals =	$695.41		$760.4428	$760.44	$760.45	$760.50