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	$119.38	6.577%	$127.2316	$127.23	$127.25	$127.20
Purchase #2	$41.76	9.404%	$45.6871	$45.69	$45.70	$45.70
Purchase #3	$131.62	7.452%	$141.4283	$141.43	$141.45	$141.40
Purchase #4	$199.65	6.772%	$213.1703	$213.17	$213.15	$213.20
Purchase #5	$206.41	3.387%	$213.4011	$213.40	$213.40	$213.40
Purchase #6	$87.87	10.623%	$97.2044	$97.20	$97.20	$97.20
Purchase #7	$162.34	3.676%	$168.3076	$168.31	$168.30	$168.30
7 purchase totals =	$949.03		$1,006.4304	$1,006.43	$1,006.45	$1,006.40