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	$143.62	8.738%	$156.1695	$156.17	$156.15	$156.20
Purchase #2	$237.87	9.843%	$261.2835	$261.28	$261.30	$261.30
Purchase #3	$175.48	4.154%	$182.7694	$182.77	$182.75	$182.80
Purchase #4	$123.87	3.270%	$127.9205	$127.92	$127.90	$127.90
Purchase #5	$201.78	4.774%	$211.413	$211.41	$211.40	$211.40
Purchase #6	$181.39	10.528%	$200.4867	$200.49	$200.50	$200.50
Purchase #7	$156.83	7.730%	$168.953	$168.95	$168.95	$169.00
7 purchase totals =	$1,220.84		$1,308.9956	$1,308.99	$1,308.95	$1,309.10