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	$208.49	3.494%	$215.7746	$215.77	$215.75	$215.80
Purchase #2	$238.93	13.816%	$271.9406	$271.94	$271.95	$271.90
Purchase #3	$244.70	6.279%	$260.0647	$260.06	$260.05	$260.10
Purchase #4	$76.87	6.765%	$82.0703	$82.07	$82.05	$82.10
Purchase #5	$178.72	12.337%	$200.7687	$200.77	$200.75	$200.80
Purchase #6	$11.71	9.152%	$12.7817	$12.78	$12.80	$12.80
Purchase #7	$152.40	6.588%	$162.4401	$162.44	$162.45	$162.40
7 purchase totals =	$1,111.82		$1,205.8407	$1,205.83	$1,205.80	$1,205.90