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	$167.71	9.107%	$182.9833	$182.98	$183.00	$183.00
Purchase #2	$45.95	7.354%	$49.3292	$49.33	$49.35	$49.30
Purchase #3	$90.88	11.458%	$101.293	$101.29	$101.30	$101.30
Purchase #4	$129.32	11.219%	$143.8284	$143.83	$143.85	$143.80
Purchase #5	$233.40	12.821%	$263.3242	$263.32	$263.30	$263.30
Purchase #6	$177.29	6.330%	$188.5125	$188.51	$188.50	$188.50
Purchase #7	$92.33	12.314%	$103.6995	$103.70	$103.70	$103.70
7 purchase totals =	$936.88		$1,032.9701	$1,032.96	$1,033.00	$1,032.90