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	$42.42	4.738%	$44.4299	$44.43	$44.45	$44.40
Purchase #2	$228.65	4.137%	$238.1093	$238.11	$238.10	$238.10
Purchase #3	$162.96	3.721%	$169.0237	$169.02	$169.00	$169.00
Purchase #4	$118.55	8.503%	$128.6303	$128.63	$128.65	$128.60
Purchase #5	$75.32	7.123%	$80.685	$80.69	$80.70	$80.70
Purchase #6	$217.82	8.868%	$237.1363	$237.14	$237.15	$237.10
Purchase #7	$74.88	7.456%	$80.4631	$80.46	$80.45	$80.50
7 purchase totals =	$920.60		$978.4776	$978.48	$978.50	$978.40