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	$118.84	8.485%	$128.9236	$128.92	$128.90	$128.90
Purchase #2	$113.86	12.379%	$127.9547	$127.95	$127.95	$128.00
Purchase #3	$171.37	13.723%	$194.8871	$194.89	$194.90	$194.90
Purchase #4	$210.94	11.787%	$235.8035	$235.80	$235.80	$235.80
Purchase #5	$29.55	9.604%	$32.388	$32.39	$32.40	$32.40
Purchase #6	$55.50	6.361%	$59.0304	$59.03	$59.05	$59.00
Purchase #7	$205.38	13.645%	$233.4041	$233.40	$233.40	$233.40
7 purchase totals =	$905.44		$1,012.3914	$1,012.38	$1,012.40	$1,012.40