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	$51.75	6.549%	$55.1391	$55.14	$55.15	$55.10
Purchase #2	$58.82	11.351%	$65.4967	$65.50	$65.50	$65.50
Purchase #3	$74.32	6.172%	$78.907	$78.91	$78.90	$78.90
Purchase #4	$22.28	5.547%	$23.5159	$23.52	$23.50	$23.50
Purchase #5	$69.61	7.197%	$74.6198	$74.62	$74.60	$74.60
Purchase #6	$29.88	12.861%	$33.7229	$33.72	$33.70	$33.70
Purchase #7	$120.87	8.501%	$131.1452	$131.15	$131.15	$131.10
7 purchase totals =	$427.53		$462.5466	$462.56	$462.50	$462.40