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	$79.35	4.449%	$82.8803	$82.88	$82.90	$82.90
Purchase #2	$140.94	8.249%	$152.5661	$152.57	$152.55	$152.60
Purchase #3	$12.31	8.874%	$13.4024	$13.40	$13.40	$13.40
Purchase #4	$92.33	7.302%	$99.0719	$99.07	$99.05	$99.10
Purchase #5	$156.57	9.735%	$171.8121	$171.81	$171.80	$171.80
Purchase #6	$85.46	3.461%	$88.4178	$88.42	$88.40	$88.40
Purchase #7	$13.41	4.595%	$14.0262	$14.03	$14.05	$14.00
7 purchase totals =	$580.37		$622.1768	$622.18	$622.15	$622.20