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	$131.63	7.414%	$141.389	$141.39	$141.40	$141.40
Purchase #2	$238.82	8.330%	$258.7137	$258.71	$258.70	$258.70
Purchase #3	$67.49	5.625%	$71.2863	$71.29	$71.30	$71.30
Purchase #4	$80.35	7.747%	$86.5747	$86.57	$86.55	$86.60
Purchase #5	$188.52	12.611%	$212.2943	$212.29	$212.30	$212.30
Purchase #6	$231.39	11.589%	$258.2058	$258.21	$258.20	$258.20
Purchase #7	$151.52	10.843%	$167.9493	$167.95	$167.95	$167.90
7 purchase totals =	$1,089.72		$1,196.4131	$1,196.41	$1,196.40	$1,196.40