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	$182.46	10.826%	$202.2131	$202.21	$202.20	$202.20
Purchase #2	$229.50	10.489%	$253.5723	$253.57	$253.55	$253.60
Purchase #3	$80.79	10.563%	$89.3238	$89.32	$89.30	$89.30
Purchase #4	$123.56	13.403%	$140.1207	$140.12	$140.10	$140.10
Purchase #5	$229.76	13.739%	$261.3267	$261.33	$261.35	$261.30
Purchase #6	$82.86	3.771%	$85.9847	$85.98	$86.00	$86.00
Purchase #7	$169.69	9.192%	$185.2879	$185.29	$185.30	$185.30
7 purchase totals =	$1,098.62		$1,217.8292	$1,217.82	$1,217.80	$1,217.80