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	$38.92	7.666%	$41.9036	$41.90	$41.90	$41.90
Purchase #2	$228.53	7.437%	$245.5258	$245.53	$245.55	$245.50
Purchase #3	$216.48	12.547%	$243.6417	$243.64	$243.65	$243.60
Purchase #4	$204.67	13.542%	$232.3864	$232.39	$232.40	$232.40
Purchase #5	$95.25	4.233%	$99.2819	$99.28	$99.30	$99.30
Purchase #6	$72.64	8.391%	$78.7352	$78.74	$78.75	$78.70
Purchase #7	$140.75	3.237%	$145.3061	$145.31	$145.30	$145.30
7 purchase totals =	$997.24		$1,086.7807	$1,086.79	$1,086.85	$1,086.70