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	$26.25	13.652%	$29.8337	$29.83	$29.85	$29.80
Purchase #2	$40.46	12.668%	$45.5855	$45.59	$45.60	$45.60
Purchase #3	$195.43	4.821%	$204.8517	$204.85	$204.85	$204.90
Purchase #4	$38.67	6.692%	$41.2578	$41.26	$41.25	$41.30
Purchase #5	$196.49	4.850%	$206.0198	$206.02	$206.00	$206.00
Purchase #6	$138.89	9.172%	$151.629	$151.63	$151.65	$151.60
Purchase #7	$42.38	9.345%	$46.3404	$46.34	$46.35	$46.30
7 purchase totals =	$678.57		$725.5179	$725.52	$725.55	$725.50