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	$32.72	13.127%	$37.0152	$37.02	$37.00	$37.00
Purchase #2	$216.36	6.226%	$229.8306	$229.83	$229.85	$229.80
Purchase #3	$45.75	4.272%	$47.7044	$47.70	$47.70	$47.70
Purchase #4	$152.47	12.796%	$171.9801	$171.98	$172.00	$172.00
Purchase #5	$142.71	6.601%	$152.1303	$152.13	$152.15	$152.10
Purchase #6	$37.94	13.464%	$43.0482	$43.05	$43.05	$43.00
Purchase #7	$90.59	6.570%	$96.5418	$96.54	$96.55	$96.50
7 purchase totals =	$718.54		$778.2506	$778.25	$778.30	$778.10