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	$212.37	4.751%	$222.4597	$222.46	$222.45	$222.50
Purchase #2	$102.74	6.524%	$109.4428	$109.44	$109.45	$109.40
Purchase #3	$55.56	10.344%	$61.3071	$61.31	$61.30	$61.30
Purchase #4	$163.39	7.391%	$175.4662	$175.47	$175.45	$175.50
Purchase #5	$81.94	9.335%	$89.5891	$89.59	$89.60	$89.60
Purchase #6	$153.45	5.757%	$162.2841	$162.28	$162.30	$162.30
Purchase #7	$246.25	3.462%	$254.7752	$254.78	$254.80	$254.80
7 purchase totals =	$1,015.70		$1,075.3242	$1,075.33	$1,075.35	$1,075.40