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	$150.84	12.434%	$169.5954	$169.60	$169.60	$169.60
Purchase #2	$104.99	4.474%	$109.6873	$109.69	$109.70	$109.70
Purchase #3	$232.63	9.454%	$254.6228	$254.62	$254.60	$254.60
Purchase #4	$228.27	11.732%	$255.0506	$255.05	$255.05	$255.10
Purchase #5	$80.58	11.372%	$89.7436	$89.74	$89.75	$89.70
Purchase #6	$141.39	9.498%	$154.8192	$154.82	$154.80	$154.80
Purchase #7	$13.71	12.355%	$15.4039	$15.40	$15.40	$15.40
7 purchase totals =	$952.41		$1,048.9228	$1,048.92	$1,048.90	$1,048.90