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	$23.77	6.313%	$25.2706	$25.27	$25.25	$25.30
Purchase #2	$241.83	13.213%	$273.783	$273.78	$273.80	$273.80
Purchase #3	$187.44	3.798%	$194.559	$194.56	$194.55	$194.60
Purchase #4	$47.48	7.131%	$50.8658	$50.87	$50.85	$50.90
Purchase #5	$136.77	11.331%	$152.2674	$152.27	$152.25	$152.30
Purchase #6	$245.43	6.752%	$262.0014	$262.00	$262.00	$262.00
Purchase #7	$90.39	4.516%	$94.472	$94.47	$94.45	$94.50
7 purchase totals =	$973.11		$1,053.2192	$1,053.22	$1,053.15	$1,053.40