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	$25.54	12.496%	$28.7315	$28.73	$28.75	$28.70
Purchase #2	$33.60	11.765%	$37.553	$37.55	$37.55	$37.60
Purchase #3	$231.71	3.660%	$240.1906	$240.19	$240.20	$240.20
Purchase #4	$247.36	8.119%	$267.4432	$267.44	$267.45	$267.40
Purchase #5	$243.84	10.257%	$268.8507	$268.85	$268.85	$268.90
Purchase #6	$134.35	11.850%	$150.2705	$150.27	$150.25	$150.30
Purchase #7	$112.88	3.549%	$116.8861	$116.89	$116.90	$116.90
7 purchase totals =	$1,029.28		$1,109.9256	$1,109.92	$1,109.95	$1,110.00