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	$81.72	4.694%	$85.5559	$85.56	$85.55	$85.60
Purchase #2	$7.45	7.156%	$7.9831	$7.98	$8.00	$8.00
Purchase #3	$102.47	12.818%	$115.6046	$115.60	$115.60	$115.60
Purchase #4	$53.92	10.493%	$59.5778	$59.58	$59.60	$59.60
Purchase #5	$130.38	7.497%	$140.1546	$140.15	$140.15	$140.20
Purchase #6	$148.50	5.263%	$156.3156	$156.32	$156.30	$156.30
Purchase #7	$219.93	10.788%	$243.656	$243.66	$243.65	$243.70
7 purchase totals =	$744.37		$808.8476	$808.85	$808.85	$809.00