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	$13.49	10.155%	$14.8599	$14.86	$14.85	$14.90
Purchase #2	$196.26	9.679%	$215.256	$215.26	$215.25	$215.30
Purchase #3	$245.56	13.232%	$278.0525	$278.05	$278.05	$278.10
Purchase #4	$63.72	4.251%	$66.4287	$66.43	$66.45	$66.40
Purchase #5	$186.30	5.289%	$196.1534	$196.15	$196.15	$196.20
Purchase #6	$195.66	10.325%	$215.8619	$215.86	$215.85	$215.90
Purchase #7	$82.54	11.288%	$91.8571	$91.86	$91.85	$91.90
7 purchase totals =	$983.53		$1,078.4695	$1,078.47	$1,078.45	$1,078.70