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	$93.82	10.350%	$103.5304	$103.53	$103.55	$103.50
Purchase #2	$228.79	4.393%	$238.8407	$238.84	$238.85	$238.80
Purchase #3	$37.40	11.360%	$41.6486	$41.65	$41.65	$41.60
Purchase #4	$228.59	9.666%	$250.6855	$250.69	$250.70	$250.70
Purchase #5	$93.30	11.281%	$103.8252	$103.83	$103.85	$103.80
Purchase #6	$87.91	4.582%	$91.938	$91.94	$91.95	$91.90
Purchase #7	$31.97	9.129%	$34.8885	$34.89	$34.90	$34.90
7 purchase totals =	$801.78		$865.3569	$865.37	$865.45	$865.20