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	$130.41	8.843%	$141.9422	$141.94	$141.95	$141.90
Purchase #2	$162.61	4.481%	$169.8966	$169.90	$169.90	$169.90
Purchase #3	$196.43	5.181%	$206.607	$206.61	$206.60	$206.60
Purchase #4	$16.36	13.118%	$18.5061	$18.51	$18.50	$18.50
Purchase #5	$11.79	12.512%	$13.2652	$13.27	$13.25	$13.30
Purchase #6	$30.47	6.122%	$32.3354	$32.34	$32.35	$32.30
Purchase #7	$142.88	10.747%	$158.2353	$158.24	$158.25	$158.20
7 purchase totals =	$690.95		$740.7878	$740.81	$740.80	$740.70