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	$80.57	4.511%	$84.2045	$84.20	$84.20	$84.20
Purchase #2	$100.29	13.807%	$114.137	$114.14	$114.15	$114.10
Purchase #3	$223.73	7.522%	$240.559	$240.56	$240.55	$240.60
Purchase #4	$234.90	5.841%	$248.6205	$248.62	$248.60	$248.60
Purchase #5	$117.99	11.286%	$131.3064	$131.31	$131.30	$131.30
Purchase #6	$223.61	7.723%	$240.8794	$240.88	$240.90	$240.90
Purchase #7	$111.77	10.249%	$123.2253	$123.23	$123.25	$123.20
7 purchase totals =	$1,092.86		$1,182.9321	$1,182.94	$1,182.95	$1,182.90