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	$137.42	5.678%	$145.2227	$145.22	$145.20	$145.20
Purchase #2	$151.87	13.380%	$172.1902	$172.19	$172.20	$172.20
Purchase #3	$99.45	3.349%	$102.7806	$102.78	$102.80	$102.80
Purchase #4	$74.79	5.210%	$78.6866	$78.69	$78.70	$78.70
Purchase #5	$141.89	3.470%	$146.8136	$146.81	$146.80	$146.80
Purchase #6	$240.42	4.764%	$251.8736	$251.87	$251.85	$251.90
Purchase #7	$250.82	6.638%	$267.4694	$267.47	$267.45	$267.50
7 purchase totals =	$1,096.66		$1,165.0367	$1,165.03	$1,165.00	$1,165.10