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	$225.59	3.593%	$233.6954	$233.70	$233.70	$233.70
Purchase #2	$205.97	8.623%	$223.7308	$223.73	$223.75	$223.70
Purchase #3	$47.69	6.629%	$50.8514	$50.85	$50.85	$50.90
Purchase #4	$171.96	6.141%	$182.5201	$182.52	$182.50	$182.50
Purchase #5	$96.95	13.710%	$110.2418	$110.24	$110.25	$110.20
Purchase #6	$80.45	4.451%	$84.0308	$84.03	$84.05	$84.00
Purchase #7	$119.74	9.795%	$131.4685	$131.47	$131.45	$131.50
7 purchase totals =	$948.35		$1,016.5388	$1,016.54	$1,016.55	$1,016.50