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	$54.40	12.860%	$61.3958	$61.40	$61.40	$61.40
Purchase #2	$233.38	13.561%	$265.0287	$265.03	$265.05	$265.00
Purchase #3	$184.83	6.310%	$196.4928	$196.49	$196.50	$196.50
Purchase #4	$212.50	4.593%	$222.2601	$222.26	$222.25	$222.30
Purchase #5	$202.87	6.636%	$216.3325	$216.33	$216.35	$216.30
Purchase #6	$103.53	11.834%	$115.7817	$115.78	$115.80	$115.80
Purchase #7	$141.44	11.710%	$158.0026	$158.00	$158.00	$158.00
7 purchase totals =	$1,132.95		$1,235.2942	$1,235.29	$1,235.35	$1,235.30