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	$156.27	4.670%	$163.5678	$163.57	$163.55	$163.60
Purchase #2	$174.72	7.808%	$188.3621	$188.36	$188.35	$188.40
Purchase #3	$29.53	13.658%	$33.5632	$33.56	$33.55	$33.60
Purchase #4	$126.63	10.192%	$139.5361	$139.54	$139.55	$139.50
Purchase #5	$67.68	7.145%	$72.5157	$72.52	$72.50	$72.50
Purchase #6	$32.46	8.850%	$35.3327	$35.33	$35.35	$35.30
Purchase #7	$156.83	7.678%	$168.8714	$168.87	$168.85	$168.90
7 purchase totals =	$744.12		$801.7490	$801.75	$801.70	$801.80