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	$223.53	6.580%	$238.2383	$238.24	$238.25	$238.20
Purchase #2	$58.82	8.326%	$63.7174	$63.72	$63.70	$63.70
Purchase #3	$81.60	7.489%	$87.711	$87.71	$87.70	$87.70
Purchase #4	$248.35	7.867%	$267.8877	$267.89	$267.90	$267.90
Purchase #5	$190.77	10.109%	$210.0549	$210.05	$210.05	$210.10
Purchase #6	$166.39	6.718%	$177.5681	$177.57	$177.55	$177.60
Purchase #7	$78.61	4.660%	$82.2732	$82.27	$82.25	$82.30
7 purchase totals =	$1,048.07		$1,127.4506	$1,127.45	$1,127.40	$1,127.50