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	$87.70	8.183%	$94.8765	$94.88	$94.90	$94.90
Purchase #2	$51.68	13.334%	$58.571	$58.57	$58.55	$58.60
Purchase #3	$101.48	8.333%	$109.9363	$109.94	$109.95	$109.90
Purchase #4	$161.76	6.657%	$172.5284	$172.53	$172.55	$172.50
Purchase #5	$221.67	9.736%	$243.2518	$243.25	$243.25	$243.30
Purchase #6	$141.96	6.822%	$151.6445	$151.64	$151.65	$151.60
Purchase #7	$245.36	11.847%	$274.4278	$274.43	$274.45	$274.40
7 purchase totals =	$1,011.61		$1,105.2363	$1,105.24	$1,105.30	$1,105.20