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	$54.52	4.653%	$57.0568	$57.06	$57.05	$57.10
Purchase #2	$171.56	13.391%	$194.5336	$194.53	$194.55	$194.50
Purchase #3	$44.33	3.353%	$45.8164	$45.82	$45.80	$45.80
Purchase #4	$123.48	6.236%	$131.1802	$131.18	$131.20	$131.20
Purchase #5	$182.33	3.396%	$188.5219	$188.52	$188.50	$188.50
Purchase #6	$92.36	8.812%	$100.4988	$100.50	$100.50	$100.50
Purchase #7	$246.26	4.428%	$257.1644	$257.16	$257.15	$257.20
7 purchase totals =	$914.84		$974.7721	$974.77	$974.75	$974.80