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	$215.40	3.281%	$222.4673	$222.47	$222.45	$222.50
Purchase #2	$204.96	12.177%	$229.918	$229.92	$229.90	$229.90
Purchase #3	$133.56	12.648%	$150.4527	$150.45	$150.45	$150.50
Purchase #4	$249.93	6.419%	$265.973	$265.97	$265.95	$266.00
Purchase #5	$61.84	7.739%	$66.6258	$66.63	$66.65	$66.60
Purchase #6	$31.94	3.721%	$33.1285	$33.13	$33.15	$33.10
Purchase #7	$153.77	13.262%	$174.163	$174.16	$174.15	$174.20
7 purchase totals =	$1,051.40		$1,142.7283	$1,142.73	$1,142.70	$1,142.80