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	$45.61	4.842%	$47.8184	$47.82	$47.80	$47.80
Purchase #2	$52.73	4.196%	$54.9426	$54.94	$54.95	$54.90
Purchase #3	$166.80	3.303%	$172.3094	$172.31	$172.30	$172.30
Purchase #4	$51.43	6.410%	$54.7267	$54.73	$54.75	$54.70
Purchase #5	$36.39	5.396%	$38.3536	$38.35	$38.35	$38.40
Purchase #6	$234.26	3.618%	$242.7355	$242.74	$242.75	$242.70
Purchase #7	$42.33	10.767%	$46.8877	$46.89	$46.90	$46.90
7 purchase totals =	$629.55		$657.7739	$657.78	$657.80	$657.70