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	$147.49	4.781%	$154.5415	$154.54	$154.55	$154.50
Purchase #2	$186.30	13.477%	$211.4077	$211.41	$211.40	$211.40
Purchase #3	$190.72	5.858%	$201.8924	$201.89	$201.90	$201.90
Purchase #4	$131.50	9.122%	$143.4954	$143.50	$143.50	$143.50
Purchase #5	$161.68	10.604%	$178.8245	$178.82	$178.80	$178.80
Purchase #6	$111.93	13.745%	$127.3148	$127.31	$127.30	$127.30
Purchase #7	$162.86	3.164%	$168.0129	$168.01	$168.00	$168.00
7 purchase totals =	$1,092.48		$1,185.4892	$1,185.48	$1,185.45	$1,185.40