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	$43.33	4.610%	$45.3275	$45.33	$45.35	$45.30
Purchase #2	$144.89	12.688%	$163.2736	$163.27	$163.25	$163.30
Purchase #3	$42.56	6.503%	$45.3277	$45.33	$45.35	$45.30
Purchase #4	$120.39	4.113%	$125.3416	$125.34	$125.35	$125.30
Purchase #5	$118.95	4.694%	$124.5335	$124.53	$124.55	$124.50
Purchase #6	$42.48	4.796%	$44.5173	$44.52	$44.50	$44.50
Purchase #7	$53.80	6.342%	$57.212	$57.21	$57.20	$57.20
7 purchase totals =	$566.40		$605.5332	$605.53	$605.55	$605.40