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	$31.72	4.185%	$33.0475	$33.05	$33.05	$33.00
Purchase #2	$59.82	7.829%	$64.5033	$64.50	$64.50	$64.50
Purchase #3	$77.72	6.703%	$82.9296	$82.93	$82.95	$82.90
Purchase #4	$127.80	12.801%	$144.1597	$144.16	$144.15	$144.20
Purchase #5	$197.27	12.822%	$222.564	$222.56	$222.55	$222.60
Purchase #6	$7.51	10.588%	$8.3052	$8.31	$8.30	$8.30
Purchase #7	$31.76	10.463%	$35.083	$35.08	$35.10	$35.10
7 purchase totals =	$533.60		$590.5923	$590.59	$590.60	$590.60