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	$34.57	5.210%	$36.3711	$36.37	$36.35	$36.40
Purchase #2	$187.65	4.765%	$196.5915	$196.59	$196.60	$196.60
Purchase #3	$27.61	13.571%	$31.357	$31.36	$31.35	$31.40
Purchase #4	$18.30	11.645%	$20.431	$20.43	$20.45	$20.40
Purchase #5	$75.92	12.399%	$85.3333	$85.33	$85.35	$85.30
Purchase #6	$24.91	13.349%	$28.2352	$28.24	$28.25	$28.20
Purchase #7	$63.69	9.807%	$69.9361	$69.94	$69.95	$69.90
7 purchase totals =	$432.65		$468.2552	$468.26	$468.30	$468.20