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	$211.75	3.371%	$218.8881	$218.89	$218.90	$218.90
Purchase #2	$12.98	3.514%	$13.4361	$13.44	$13.45	$13.40
Purchase #3	$218.26	7.459%	$234.54	$234.54	$234.55	$234.50
Purchase #4	$108.89	5.512%	$114.892	$114.89	$114.90	$114.90
Purchase #5	$78.62	13.291%	$89.0694	$89.07	$89.05	$89.10
Purchase #6	$96.49	7.493%	$103.72	$103.72	$103.70	$103.70
Purchase #7	$28.45	6.620%	$30.3334	$30.33	$30.35	$30.30
7 purchase totals =	$755.44		$804.8790	$804.88	$804.90	$804.80