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	$96.40	9.251%	$105.318	$105.32	$105.30	$105.30
Purchase #2	$187.75	4.432%	$196.0711	$196.07	$196.05	$196.10
Purchase #3	$147.68	6.737%	$157.6292	$157.63	$157.65	$157.60
Purchase #4	$68.76	5.184%	$72.3245	$72.32	$72.30	$72.30
Purchase #5	$201.34	5.752%	$212.9211	$212.92	$212.90	$212.90
Purchase #6	$158.78	10.840%	$175.9918	$175.99	$176.00	$176.00
Purchase #7	$235.58	12.516%	$265.0652	$265.07	$265.05	$265.10
7 purchase totals =	$1,096.29		$1,185.3209	$1,185.32	$1,185.25	$1,185.30