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	$159.96	4.537%	$167.2174	$167.22	$167.20	$167.20
Purchase #2	$5.42	12.241%	$6.0835	$6.08	$6.10	$6.10
Purchase #3	$148.43	9.308%	$162.2459	$162.25	$162.25	$162.20
Purchase #4	$86.56	3.863%	$89.9038	$89.90	$89.90	$89.90
Purchase #5	$205.33	10.726%	$227.3537	$227.35	$227.35	$227.40
Purchase #6	$105.91	3.520%	$109.638	$109.64	$109.65	$109.60
Purchase #7	$19.52	4.199%	$20.3396	$20.34	$20.35	$20.30
7 purchase totals =	$731.13		$782.7819	$782.78	$782.80	$782.70