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	$170.85	7.729%	$184.055	$184.06	$184.05	$184.10
Purchase #2	$148.61	12.691%	$167.4701	$167.47	$167.45	$167.50
Purchase #3	$155.46	4.424%	$162.3376	$162.34	$162.35	$162.30
Purchase #4	$76.76	12.821%	$86.6014	$86.60	$86.60	$86.60
Purchase #5	$17.68	4.531%	$18.4811	$18.48	$18.50	$18.50
Purchase #6	$178.95	12.463%	$201.2525	$201.25	$201.25	$201.30
Purchase #7	$167.63	12.433%	$188.4714	$188.47	$188.45	$188.50
7 purchase totals =	$915.94		$1,008.6691	$1,008.67	$1,008.65	$1,008.80