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	$137.75	9.787%	$151.2316	$151.23	$151.25	$151.20
Purchase #2	$184.73	5.502%	$194.8938	$194.89	$194.90	$194.90
Purchase #3	$97.83	12.301%	$109.8641	$109.86	$109.85	$109.90
Purchase #4	$19.88	10.508%	$21.969	$21.97	$21.95	$22.00
Purchase #5	$246.62	8.515%	$267.6197	$267.62	$267.60	$267.60
Purchase #6	$243.72	7.741%	$262.5864	$262.59	$262.60	$262.60
Purchase #7	$137.33	5.157%	$144.4121	$144.41	$144.40	$144.40
7 purchase totals =	$1,067.86		$1,152.5767	$1,152.57	$1,152.55	$1,152.60