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	$75.76	4.157%	$78.9093	$78.91	$78.90	$78.90
Purchase #2	$101.93	8.196%	$110.2842	$110.28	$110.30	$110.30
Purchase #3	$250.26	6.450%	$266.4018	$266.40	$266.40	$266.40
Purchase #4	$233.37	8.559%	$253.3441	$253.34	$253.35	$253.30
Purchase #5	$13.74	11.392%	$15.3053	$15.31	$15.30	$15.30
Purchase #6	$91.34	13.754%	$103.9029	$103.90	$103.90	$103.90
Purchase #7	$171.74	8.577%	$186.4701	$186.47	$186.45	$186.50
7 purchase totals =	$938.14		$1,014.6177	$1,014.61	$1,014.60	$1,014.60