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	$211.59	13.746%	$240.6752	$240.68	$240.70	$240.70
Purchase #2	$198.77	12.478%	$223.5725	$223.57	$223.55	$223.60
Purchase #3	$132.53	3.294%	$136.8955	$136.90	$136.90	$136.90
Purchase #4	$85.38	5.813%	$90.3431	$90.34	$90.35	$90.30
Purchase #5	$107.59	7.199%	$115.3354	$115.34	$115.35	$115.30
Purchase #6	$44.40	6.241%	$47.171	$47.17	$47.15	$47.20
Purchase #7	$181.50	10.145%	$199.9132	$199.91	$199.90	$199.90
7 purchase totals =	$961.76		$1,053.9059	$1,053.91	$1,053.90	$1,053.90