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	$77.30	7.558%	$83.1423	$83.14	$83.15	$83.10
Purchase #2	$109.88	5.179%	$115.5707	$115.57	$115.55	$115.60
Purchase #3	$231.37	10.329%	$255.2682	$255.27	$255.25	$255.30
Purchase #4	$146.99	10.369%	$162.2314	$162.23	$162.25	$162.20
Purchase #5	$184.38	4.104%	$191.947	$191.95	$191.95	$191.90
Purchase #6	$100.33	12.364%	$112.7348	$112.73	$112.75	$112.70
Purchase #7	$108.32	11.740%	$121.0368	$121.04	$121.05	$121.00
7 purchase totals =	$958.57		$1,041.9312	$1,041.93	$1,041.95	$1,041.80