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	$179.54	3.392%	$185.63	$185.63	$185.65	$185.60
Purchase #2	$109.59	3.200%	$113.0969	$113.10	$113.10	$113.10
Purchase #3	$32.35	4.557%	$33.8242	$33.82	$33.80	$33.80
Purchase #4	$158.60	6.452%	$168.8329	$168.83	$168.85	$168.80
Purchase #5	$10.84	7.689%	$11.6735	$11.67	$11.65	$11.70
Purchase #6	$238.79	13.528%	$271.0935	$271.09	$271.10	$271.10
Purchase #7	$241.35	11.298%	$268.6177	$268.62	$268.60	$268.60
7 purchase totals =	$971.06		$1,052.7687	$1,052.76	$1,052.75	$1,052.70