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	$207.66	12.835%	$234.3132	$234.31	$234.30	$234.30
Purchase #2	$159.44	10.826%	$176.701	$176.70	$176.70	$176.70
Purchase #3	$239.44	4.574%	$250.392	$250.39	$250.40	$250.40
Purchase #4	$206.48	12.320%	$231.9183	$231.92	$231.90	$231.90
Purchase #5	$190.69	10.814%	$211.3112	$211.31	$211.30	$211.30
Purchase #6	$188.26	4.559%	$196.8428	$196.84	$196.85	$196.80
Purchase #7	$96.57	6.866%	$103.2005	$103.20	$103.20	$103.20
7 purchase totals =	$1,288.54		$1,404.6790	$1,404.67	$1,404.65	$1,404.60