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	$153.56	7.154%	$164.5457	$164.55	$164.55	$164.50
Purchase #2	$28.94	5.735%	$30.5997	$30.60	$30.60	$30.60
Purchase #3	$72.66	8.110%	$78.5527	$78.55	$78.55	$78.60
Purchase #4	$231.73	7.706%	$249.5871	$249.59	$249.60	$249.60
Purchase #5	$139.60	6.556%	$148.7522	$148.75	$148.75	$148.80
Purchase #6	$156.90	3.431%	$162.2832	$162.28	$162.30	$162.30
Purchase #7	$81.31	13.765%	$92.5023	$92.50	$92.50	$92.50
7 purchase totals =	$864.70		$926.8229	$926.82	$926.85	$926.90