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	$229.47	5.303%	$241.6388	$241.64	$241.65	$241.60
Purchase #2	$72.59	12.406%	$81.5955	$81.60	$81.60	$81.60
Purchase #3	$86.74	9.119%	$94.6498	$94.65	$94.65	$94.60
Purchase #4	$12.91	5.278%	$13.5914	$13.59	$13.60	$13.60
Purchase #5	$63.72	5.846%	$67.4451	$67.45	$67.45	$67.40
Purchase #6	$89.71	9.566%	$98.2917	$98.29	$98.30	$98.30
Purchase #7	$145.51	10.129%	$160.2487	$160.25	$160.25	$160.20
7 purchase totals =	$700.65		$757.4610	$757.47	$757.50	$757.30