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	$168.71	7.619%	$181.564	$181.56	$181.55	$181.60
Purchase #2	$42.58	4.231%	$44.3816	$44.38	$44.40	$44.40
Purchase #3	$106.95	5.607%	$112.9467	$112.95	$112.95	$112.90
Purchase #4	$83.61	7.126%	$89.568	$89.57	$89.55	$89.60
Purchase #5	$31.94	11.428%	$35.5901	$35.59	$35.60	$35.60
Purchase #6	$176.55	13.448%	$200.2924	$200.29	$200.30	$200.30
Purchase #7	$115.47	10.127%	$127.1636	$127.16	$127.15	$127.20
7 purchase totals =	$725.81		$791.5064	$791.50	$791.50	$791.60