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	$39.85	10.346%	$43.9729	$43.97	$43.95	$44.00
Purchase #2	$229.82	3.623%	$238.1464	$238.15	$238.15	$238.10
Purchase #3	$88.29	4.371%	$92.1492	$92.15	$92.15	$92.10
Purchase #4	$197.41	10.756%	$218.6434	$218.64	$218.65	$218.60
Purchase #5	$191.75	4.751%	$200.86	$200.86	$200.85	$200.90
Purchase #6	$224.40	6.758%	$239.565	$239.57	$239.55	$239.60
Purchase #7	$140.65	8.146%	$152.1073	$152.11	$152.10	$152.10
7 purchase totals =	$1,112.17		$1,185.4442	$1,185.45	$1,185.40	$1,185.40