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	$190.71	11.193%	$212.0562	$212.06	$212.05	$212.10
Purchase #2	$168.54	11.671%	$188.2103	$188.21	$188.20	$188.20
Purchase #3	$166.77	10.318%	$183.9773	$183.98	$184.00	$184.00
Purchase #4	$196.65	11.692%	$219.6423	$219.64	$219.65	$219.60
Purchase #5	$26.55	10.258%	$29.2735	$29.27	$29.25	$29.30
Purchase #6	$163.52	11.336%	$182.0566	$182.06	$182.05	$182.10
Purchase #7	$79.45	13.575%	$90.2353	$90.24	$90.25	$90.20
7 purchase totals =	$992.19		$1,105.4515	$1,105.46	$1,105.45	$1,105.50