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	$100.85	8.153%	$109.0723	$109.07	$109.05	$109.10
Purchase #2	$57.82	6.259%	$61.439	$61.44	$61.45	$61.40
Purchase #3	$232.79	10.361%	$256.9094	$256.91	$256.90	$256.90
Purchase #4	$162.72	5.404%	$171.5134	$171.51	$171.50	$171.50
Purchase #5	$168.65	12.470%	$189.6807	$189.68	$189.70	$189.70
Purchase #6	$109.93	5.138%	$115.5782	$115.58	$115.60	$115.60
Purchase #7	$198.74	4.535%	$207.7529	$207.75	$207.75	$207.80
7 purchase totals =	$1,031.50		$1,111.9459	$1,111.94	$1,111.95	$1,112.00