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	$105.54	11.351%	$117.5198	$117.52	$117.50	$117.50
Purchase #2	$135.30	11.764%	$151.2167	$151.22	$151.20	$151.20
Purchase #3	$98.28	10.770%	$108.8648	$108.86	$108.85	$108.90
Purchase #4	$180.64	11.322%	$201.0921	$201.09	$201.10	$201.10
Purchase #5	$145.77	9.807%	$160.0657	$160.07	$160.05	$160.10
Purchase #6	$152.38	12.793%	$171.874	$171.87	$171.85	$171.90
Purchase #7	$114.40	11.868%	$127.977	$127.98	$128.00	$128.00
7 purchase totals =	$932.31		$1,038.6101	$1,038.61	$1,038.55	$1,038.70