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	$143.47	10.519%	$158.5616	$158.56	$158.55	$158.60
Purchase #2	$158.69	12.291%	$178.1946	$178.19	$178.20	$178.20
Purchase #3	$78.65	5.711%	$83.1417	$83.14	$83.15	$83.10
Purchase #4	$77.46	8.328%	$83.9109	$83.91	$83.90	$83.90
Purchase #5	$170.68	9.648%	$187.1472	$187.15	$187.15	$187.10
Purchase #6	$90.44	10.743%	$100.156	$100.16	$100.15	$100.20
Purchase #7	$104.87	4.258%	$109.3354	$109.34	$109.35	$109.30
7 purchase totals =	$824.26		$900.4474	$900.45	$900.45	$900.40