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	$43.44	11.759%	$48.5481	$48.55	$48.55	$48.50
Purchase #2	$172.93	12.445%	$194.4511	$194.45	$194.45	$194.50
Purchase #3	$76.82	5.618%	$81.1357	$81.14	$81.15	$81.10
Purchase #4	$77.58	11.445%	$86.459	$86.46	$86.45	$86.50
Purchase #5	$99.74	7.758%	$107.4778	$107.48	$107.50	$107.50
Purchase #6	$169.34	13.651%	$192.4566	$192.46	$192.45	$192.50
Purchase #7	$39.63	5.774%	$41.9182	$41.92	$41.90	$41.90
7 purchase totals =	$679.48		$752.4465	$752.46	$752.45	$752.50