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	$33.30	10.177%	$36.6889	$36.69	$36.70	$36.70
Purchase #2	$103.62	7.448%	$111.3376	$111.34	$111.35	$111.30
Purchase #3	$9.86	10.562%	$10.9014	$10.90	$10.90	$10.90
Purchase #4	$83.34	12.840%	$94.0409	$94.04	$94.05	$94.00
Purchase #5	$38.54	10.505%	$42.5886	$42.59	$42.60	$42.60
Purchase #6	$171.30	13.317%	$194.112	$194.11	$194.10	$194.10
Purchase #7	$95.26	3.147%	$98.2578	$98.26	$98.25	$98.30
7 purchase totals =	$535.22		$587.9272	$587.93	$587.95	$587.90