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	$153.62	12.272%	$172.4722	$172.47	$172.45	$172.50
Purchase #2	$44.95	13.268%	$50.914	$50.91	$50.90	$50.90
Purchase #3	$33.88	4.781%	$35.4998	$35.50	$35.50	$35.50
Purchase #4	$153.51	13.373%	$174.0389	$174.04	$174.05	$174.00
Purchase #5	$229.61	3.714%	$238.1377	$238.14	$238.15	$238.10
Purchase #6	$183.47	6.874%	$196.0817	$196.08	$196.10	$196.10
Purchase #7	$224.25	9.453%	$245.4484	$245.45	$245.45	$245.40
7 purchase totals =	$1,023.29		$1,112.5927	$1,112.59	$1,112.60	$1,112.50