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	$184.76	8.137%	$199.7939	$199.79	$199.80	$199.80
Purchase #2	$6.54	11.246%	$7.2755	$7.28	$7.30	$7.30
Purchase #3	$101.32	10.119%	$111.5726	$111.57	$111.55	$111.60
Purchase #4	$156.70	6.764%	$167.2992	$167.30	$167.30	$167.30
Purchase #5	$71.88	9.150%	$78.457	$78.46	$78.45	$78.50
Purchase #6	$111.52	13.586%	$126.6711	$126.67	$126.65	$126.70
Purchase #7	$166.64	9.238%	$182.0342	$182.03	$182.05	$182.00
7 purchase totals =	$799.36		$873.1035	$873.10	$873.10	$873.20