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	$190.54	11.304%	$212.0786	$212.08	$212.10	$212.10
Purchase #2	$207.65	4.170%	$216.309	$216.31	$216.30	$216.30
Purchase #3	$191.87	4.755%	$200.9934	$200.99	$201.00	$201.00
Purchase #4	$215.67	7.120%	$231.0257	$231.03	$231.05	$231.00
Purchase #5	$118.71	10.391%	$131.0452	$131.05	$131.05	$131.00
Purchase #6	$71.29	10.552%	$78.8125	$78.81	$78.80	$78.80
Purchase #7	$170.96	8.534%	$185.5497	$185.55	$185.55	$185.50
7 purchase totals =	$1,166.69		$1,255.8141	$1,255.82	$1,255.85	$1,255.70