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	$70.94	11.676%	$79.223	$79.22	$79.20	$79.20
Purchase #2	$65.85	11.719%	$73.567	$73.57	$73.55	$73.60
Purchase #3	$145.52	4.674%	$152.3216	$152.32	$152.30	$152.30
Purchase #4	$174.25	9.308%	$190.4692	$190.47	$190.45	$190.50
Purchase #5	$215.52	3.734%	$223.5675	$223.57	$223.55	$223.60
Purchase #6	$36.80	7.143%	$39.4286	$39.43	$39.45	$39.40
Purchase #7	$130.26	10.115%	$143.4358	$143.44	$143.45	$143.40
7 purchase totals =	$839.14		$902.0127	$902.02	$901.95	$902.00