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	$43.61	3.803%	$45.2685	$45.27	$45.25	$45.30
Purchase #2	$241.40	9.372%	$264.024	$264.02	$264.00	$264.00
Purchase #3	$19.74	4.609%	$20.6498	$20.65	$20.65	$20.60
Purchase #4	$20.27	5.269%	$21.338	$21.34	$21.35	$21.30
Purchase #5	$12.79	10.752%	$14.1652	$14.17	$14.15	$14.20
Purchase #6	$10.96	8.600%	$11.9026	$11.90	$11.90	$11.90
Purchase #7	$21.58	13.728%	$24.5425	$24.54	$24.55	$24.50
7 purchase totals =	$370.35		$401.8906	$401.89	$401.85	$401.80