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	$79.25	10.459%	$87.5388	$87.54	$87.55	$87.50
Purchase #2	$120.63	8.646%	$131.0597	$131.06	$131.05	$131.10
Purchase #3	$71.92	9.604%	$78.8272	$78.83	$78.85	$78.80
Purchase #4	$159.85	11.619%	$178.423	$178.42	$178.40	$178.40
Purchase #5	$157.98	6.587%	$168.3861	$168.39	$168.40	$168.40
Purchase #6	$84.40	8.671%	$91.7183	$91.72	$91.70	$91.70
Purchase #7	$188.26	11.377%	$209.6783	$209.68	$209.70	$209.70
7 purchase totals =	$862.29		$945.6314	$945.64	$945.65	$945.60