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	$35.98	11.359%	$40.067	$40.07	$40.05	$40.10
Purchase #2	$239.77	6.111%	$254.4223	$254.42	$254.40	$254.40
Purchase #3	$109.43	8.253%	$118.4613	$118.46	$118.45	$118.50
Purchase #4	$12.73	9.263%	$13.9092	$13.91	$13.90	$13.90
Purchase #5	$209.82	6.251%	$222.9358	$222.94	$222.95	$222.90
Purchase #6	$162.70	11.102%	$180.763	$180.76	$180.75	$180.80
Purchase #7	$96.26	6.870%	$102.8731	$102.87	$102.85	$102.90
7 purchase totals =	$866.69		$933.4317	$933.43	$933.35	$933.50