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	$200.95	9.790%	$220.623	$220.62	$220.60	$220.60
Purchase #2	$169.33	11.865%	$189.421	$189.42	$189.40	$189.40
Purchase #3	$185.88	11.141%	$206.5889	$206.59	$206.60	$206.60
Purchase #4	$18.81	8.789%	$20.4632	$20.46	$20.45	$20.50
Purchase #5	$145.55	7.783%	$156.8782	$156.88	$156.90	$156.90
Purchase #6	$25.42	11.810%	$28.4221	$28.42	$28.40	$28.40
Purchase #7	$126.85	3.589%	$131.4026	$131.40	$131.40	$131.40
7 purchase totals =	$872.79		$953.7990	$953.79	$953.75	$953.80