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	$139.79	7.512%	$150.291	$150.29	$150.30	$150.30
Purchase #2	$186.93	10.789%	$207.0979	$207.10	$207.10	$207.10
Purchase #3	$59.37	4.290%	$61.917	$61.92	$61.90	$61.90
Purchase #4	$86.96	6.520%	$92.6298	$92.63	$92.65	$92.60
Purchase #5	$85.81	4.263%	$89.4681	$89.47	$89.45	$89.50
Purchase #6	$28.96	5.622%	$30.5881	$30.59	$30.60	$30.60
Purchase #7	$186.60	7.534%	$200.6584	$200.66	$200.65	$200.70
7 purchase totals =	$774.42		$832.6503	$832.66	$832.65	$832.70