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	$111.38	9.611%	$122.0847	$122.08	$122.10	$122.10
Purchase #2	$84.75	5.620%	$89.513	$89.51	$89.50	$89.50
Purchase #3	$227.36	5.732%	$240.3923	$240.39	$240.40	$240.40
Purchase #4	$88.55	12.534%	$99.6489	$99.65	$99.65	$99.60
Purchase #5	$41.85	4.277%	$43.6399	$43.64	$43.65	$43.60
Purchase #6	$83.60	13.790%	$95.1284	$95.13	$95.15	$95.10
Purchase #7	$240.37	4.787%	$251.8765	$251.88	$251.90	$251.90
7 purchase totals =	$877.86		$942.2837	$942.28	$942.35	$942.20