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	$225.31	7.743%	$242.7558	$242.76	$242.75	$242.80
Purchase #2	$48.99	11.166%	$54.4602	$54.46	$54.45	$54.50
Purchase #3	$233.35	3.462%	$241.4286	$241.43	$241.45	$241.40
Purchase #4	$181.69	8.245%	$196.6703	$196.67	$196.65	$196.70
Purchase #5	$92.36	7.521%	$99.3064	$99.31	$99.30	$99.30
Purchase #6	$27.41	11.496%	$30.5611	$30.56	$30.55	$30.60
Purchase #7	$44.37	8.178%	$47.9986	$48.00	$48.00	$48.00
7 purchase totals =	$853.48		$913.1810	$913.19	$913.15	$913.30