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	$99.28	10.429%	$109.6339	$109.63	$109.65	$109.60
Purchase #2	$68.58	12.645%	$77.2519	$77.25	$77.25	$77.30
Purchase #3	$30.96	3.738%	$32.1173	$32.12	$32.10	$32.10
Purchase #4	$49.77	7.825%	$53.6645	$53.66	$53.65	$53.70
Purchase #5	$50.77	5.818%	$53.7238	$53.72	$53.70	$53.70
Purchase #6	$55.88	12.444%	$62.8337	$62.83	$62.85	$62.80
Purchase #7	$45.56	7.337%	$48.9027	$48.90	$48.90	$48.90
7 purchase totals =	$400.80		$438.1278	$438.11	$438.10	$438.10