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	$180.98	9.648%	$198.441	$198.44	$198.45	$198.40
Purchase #2	$21.56	6.463%	$22.9534	$22.95	$22.95	$23.00
Purchase #3	$155.73	3.586%	$161.3145	$161.31	$161.30	$161.30
Purchase #4	$250.75	3.434%	$259.3608	$259.36	$259.35	$259.40
Purchase #5	$30.38	10.771%	$33.6522	$33.65	$33.65	$33.70
Purchase #6	$33.86	13.741%	$38.5127	$38.51	$38.50	$38.50
Purchase #7	$99.46	12.545%	$111.9373	$111.94	$111.95	$111.90
7 purchase totals =	$772.72		$826.1719	$826.16	$826.15	$826.20