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	$118.86	10.267%	$131.0634	$131.06	$131.05	$131.10
Purchase #2	$99.62	13.783%	$113.3506	$113.35	$113.35	$113.40
Purchase #3	$228.52	3.175%	$235.7755	$235.78	$235.80	$235.80
Purchase #4	$128.82	12.209%	$144.5476	$144.55	$144.55	$144.50
Purchase #5	$248.37	3.583%	$257.2691	$257.27	$257.25	$257.30
Purchase #6	$223.52	13.557%	$253.8226	$253.82	$253.80	$253.80
Purchase #7	$213.81	4.263%	$222.9247	$222.92	$222.90	$222.90
7 purchase totals =	$1,261.52		$1,358.7535	$1,358.75	$1,358.70	$1,358.80