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	$102.48	7.274%	$109.9344	$109.93	$109.95	$109.90
Purchase #2	$99.55	7.299%	$106.8162	$106.82	$106.80	$106.80
Purchase #3	$111.36	3.744%	$115.5293	$115.53	$115.55	$115.50
Purchase #4	$113.53	12.872%	$128.1436	$128.14	$128.15	$128.10
Purchase #5	$104.29	3.342%	$107.7754	$107.78	$107.80	$107.80
Purchase #6	$131.59	12.663%	$148.2532	$148.25	$148.25	$148.30
Purchase #7	$37.85	10.824%	$41.9469	$41.95	$41.95	$41.90
7 purchase totals =	$700.65		$758.3990	$758.40	$758.45	$758.30