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	$13.50	3.765%	$14.0083	$14.01	$14.00	$14.00
Purchase #2	$115.73	9.543%	$126.7741	$126.77	$126.75	$126.80
Purchase #3	$83.70	7.115%	$89.6553	$89.66	$89.65	$89.70
Purchase #4	$48.80	4.405%	$50.9496	$50.95	$50.95	$50.90
Purchase #5	$104.63	7.385%	$112.3569	$112.36	$112.35	$112.40
Purchase #6	$42.47	6.592%	$45.2696	$45.27	$45.25	$45.30
Purchase #7	$57.70	6.122%	$61.2324	$61.23	$61.25	$61.20
7 purchase totals =	$466.53		$500.2462	$500.25	$500.20	$500.30