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	$233.44	4.427%	$243.7744	$243.77	$243.75	$243.80
Purchase #2	$17.50	6.517%	$18.6405	$18.64	$18.65	$18.60
Purchase #3	$25.28	12.665%	$28.4817	$28.48	$28.50	$28.50
Purchase #4	$249.94	12.737%	$281.7749	$281.77	$281.75	$281.80
Purchase #5	$240.56	10.277%	$265.2824	$265.28	$265.30	$265.30
Purchase #6	$102.25	5.770%	$108.1498	$108.15	$108.15	$108.10
Purchase #7	$101.77	13.539%	$115.5486	$115.55	$115.55	$115.50
7 purchase totals =	$970.74		$1,061.6523	$1,061.64	$1,061.65	$1,061.60