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	$240.26	11.674%	$268.308	$268.31	$268.30	$268.30
Purchase #2	$93.92	10.419%	$103.7055	$103.71	$103.70	$103.70
Purchase #3	$90.99	12.294%	$102.1763	$102.18	$102.20	$102.20
Purchase #4	$224.58	11.421%	$250.2293	$250.23	$250.25	$250.20
Purchase #5	$195.34	13.789%	$222.2754	$222.28	$222.30	$222.30
Purchase #6	$105.62	6.657%	$112.6511	$112.65	$112.65	$112.70
Purchase #7	$51.34	11.292%	$57.1373	$57.14	$57.15	$57.10
7 purchase totals =	$1,002.05		$1,116.4829	$1,116.50	$1,116.55	$1,116.50