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	$174.75	4.434%	$182.4984	$182.50	$182.50	$182.50
Purchase #2	$28.46	13.653%	$32.3456	$32.35	$32.35	$32.30
Purchase #3	$78.31	5.790%	$82.8441	$82.84	$82.85	$82.80
Purchase #4	$183.64	11.619%	$204.9771	$204.98	$205.00	$205.00
Purchase #5	$220.81	13.462%	$250.5354	$250.54	$250.55	$250.50
Purchase #6	$141.35	13.441%	$160.3489	$160.35	$160.35	$160.30
Purchase #7	$216.63	4.540%	$226.465	$226.47	$226.45	$226.50
7 purchase totals =	$1,043.95		$1,140.0145	$1,140.03	$1,140.05	$1,139.90