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	$232.98	7.696%	$250.9101	$250.91	$250.90	$250.90
Purchase #2	$6.88	7.547%	$7.3992	$7.40	$7.40	$7.40
Purchase #3	$95.55	4.553%	$99.9004	$99.90	$99.90	$99.90
Purchase #4	$144.36	12.815%	$162.8597	$162.86	$162.85	$162.90
Purchase #5	$26.32	9.529%	$28.828	$28.83	$28.85	$28.80
Purchase #6	$161.78	8.680%	$175.8225	$175.82	$175.80	$175.80
Purchase #7	$153.95	13.720%	$175.0719	$175.07	$175.05	$175.10
7 purchase totals =	$821.82		$900.7918	$900.79	$900.75	$900.80