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	$86.48	3.333%	$89.3624	$89.36	$89.35	$89.40
Purchase #2	$103.33	7.438%	$111.0157	$111.02	$111.00	$111.00
Purchase #3	$42.56	10.478%	$47.0194	$47.02	$47.00	$47.00
Purchase #4	$82.41	3.241%	$85.0809	$85.08	$85.10	$85.10
Purchase #5	$134.91	12.867%	$152.2689	$152.27	$152.25	$152.30
Purchase #6	$245.63	10.808%	$272.1777	$272.18	$272.20	$272.20
Purchase #7	$91.46	7.855%	$98.6442	$98.64	$98.65	$98.60
7 purchase totals =	$786.78		$855.5692	$855.57	$855.55	$855.60