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	$220.51	3.643%	$228.5432	$228.54	$228.55	$228.50
Purchase #2	$86.68	3.240%	$89.4884	$89.49	$89.50	$89.50
Purchase #3	$113.58	8.344%	$123.0571	$123.06	$123.05	$123.10
Purchase #4	$50.45	5.592%	$53.2712	$53.27	$53.25	$53.30
Purchase #5	$137.80	9.835%	$151.3526	$151.35	$151.35	$151.40
Purchase #6	$99.91	6.617%	$106.521	$106.52	$106.50	$106.50
Purchase #7	$20.96	5.364%	$22.0843	$22.08	$22.10	$22.10
7 purchase totals =	$729.89		$774.3178	$774.31	$774.30	$774.40