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	$41.60	9.363%	$45.495	$45.50	$45.50	$45.50
Purchase #2	$188.71	5.691%	$199.4495	$199.45	$199.45	$199.40
Purchase #3	$196.72	3.473%	$203.5521	$203.55	$203.55	$203.60
Purchase #4	$211.79	11.225%	$235.5634	$235.56	$235.55	$235.60
Purchase #5	$51.91	3.611%	$53.7845	$53.78	$53.80	$53.80
Purchase #6	$92.90	5.772%	$98.2622	$98.26	$98.25	$98.30
Purchase #7	$164.86	4.166%	$171.7281	$171.73	$171.75	$171.70
7 purchase totals =	$948.49		$1,007.8348	$1,007.83	$1,007.85	$1,007.90