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	$185.59	5.869%	$196.4823	$196.48	$196.50	$196.50
Purchase #2	$131.49	12.816%	$148.3418	$148.34	$148.35	$148.30
Purchase #3	$89.64	3.776%	$93.0248	$93.02	$93.00	$93.00
Purchase #4	$103.73	13.572%	$117.8082	$117.81	$117.80	$117.80
Purchase #5	$88.56	11.636%	$98.8648	$98.86	$98.85	$98.90
Purchase #6	$202.31	5.785%	$214.0136	$214.01	$214.00	$214.00
Purchase #7	$69.27	11.372%	$77.1474	$77.15	$77.15	$77.10
7 purchase totals =	$870.59		$945.6829	$945.67	$945.65	$945.60