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	$186.32	4.539%	$194.7771	$194.78	$194.80	$194.80
Purchase #2	$40.65	12.225%	$45.6195	$45.62	$45.60	$45.60
Purchase #3	$87.42	9.860%	$96.0396	$96.04	$96.05	$96.00
Purchase #4	$159.82	3.820%	$165.9251	$165.93	$165.95	$165.90
Purchase #5	$202.96	9.174%	$221.5796	$221.58	$221.60	$221.60
Purchase #6	$212.53	12.404%	$238.8922	$238.89	$238.90	$238.90
Purchase #7	$68.55	7.743%	$73.8578	$73.86	$73.85	$73.90
7 purchase totals =	$958.25		$1,036.6909	$1,036.70	$1,036.75	$1,036.70