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	$86.54	12.126%	$97.0338	$97.03	$97.05	$97.00
Purchase #2	$128.72	10.637%	$142.4119	$142.41	$142.40	$142.40
Purchase #3	$215.99	5.513%	$227.8975	$227.90	$227.90	$227.90
Purchase #4	$168.56	11.819%	$188.4821	$188.48	$188.50	$188.50
Purchase #5	$42.47	9.843%	$46.6503	$46.65	$46.65	$46.70
Purchase #6	$19.72	4.784%	$20.6634	$20.66	$20.65	$20.70
Purchase #7	$111.40	11.168%	$123.8412	$123.84	$123.85	$123.80
7 purchase totals =	$773.40		$846.9802	$846.97	$847.00	$847.00