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	$156.81	10.253%	$172.8877	$172.89	$172.90	$172.90
Purchase #2	$112.65	5.872%	$119.2648	$119.26	$119.25	$119.30
Purchase #3	$128.30	6.235%	$136.2995	$136.30	$136.30	$136.30
Purchase #4	$178.92	5.688%	$189.097	$189.10	$189.10	$189.10
Purchase #5	$152.44	11.172%	$169.4706	$169.47	$169.45	$169.50
Purchase #6	$51.35	4.872%	$53.8518	$53.85	$53.85	$53.90
Purchase #7	$12.35	9.722%	$13.5507	$13.55	$13.55	$13.60
7 purchase totals =	$792.82		$854.4221	$854.42	$854.40	$854.60