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	$128.55	9.206%	$140.3843	$140.38	$140.40	$140.40
Purchase #2	$156.72	3.461%	$162.1441	$162.14	$162.15	$162.10
Purchase #3	$29.55	5.342%	$31.1286	$31.13	$31.15	$31.10
Purchase #4	$139.50	11.303%	$155.2677	$155.27	$155.25	$155.30
Purchase #5	$86.75	3.439%	$89.7333	$89.73	$89.75	$89.70
Purchase #6	$206.45	13.117%	$233.53	$233.53	$233.55	$233.50
Purchase #7	$243.51	9.203%	$265.9202	$265.92	$265.90	$265.90
7 purchase totals =	$991.03		$1,078.1082	$1,078.10	$1,078.15	$1,078.00