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	$218.64	10.374%	$241.3217	$241.32	$241.30	$241.30
Purchase #2	$10.64	3.150%	$10.9752	$10.98	$11.00	$11.00
Purchase #3	$177.45	6.305%	$188.6382	$188.64	$188.65	$188.60
Purchase #4	$51.26	12.535%	$57.6854	$57.69	$57.70	$57.70
Purchase #5	$137.59	13.298%	$155.8867	$155.89	$155.90	$155.90
Purchase #6	$69.75	13.148%	$78.9207	$78.92	$78.90	$78.90
Purchase #7	$223.28	6.349%	$237.456	$237.46	$237.45	$237.50
7 purchase totals =	$888.61		$970.8839	$970.90	$970.90	$970.90