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	$103.74	6.426%	$110.4063	$110.41	$110.40	$110.40
Purchase #2	$213.96	3.217%	$220.8431	$220.84	$220.85	$220.80
Purchase #3	$51.66	5.253%	$54.3737	$54.37	$54.35	$54.40
Purchase #4	$231.43	10.748%	$256.3041	$256.30	$256.30	$256.30
Purchase #5	$239.37	5.699%	$253.0117	$253.01	$253.00	$253.00
Purchase #6	$38.63	7.300%	$41.45	$41.45	$41.45	$41.50
Purchase #7	$99.78	9.343%	$109.1024	$109.10	$109.10	$109.10
7 purchase totals =	$978.57		$1,045.4913	$1,045.48	$1,045.45	$1,045.50