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	$168.59	10.152%	$185.7053	$185.71	$185.70	$185.70
Purchase #2	$41.63	8.275%	$45.0749	$45.07	$45.05	$45.10
Purchase #3	$37.70	3.253%	$38.9264	$38.93	$38.95	$38.90
Purchase #4	$224.80	10.638%	$248.7142	$248.71	$248.70	$248.70
Purchase #5	$199.83	4.777%	$209.3759	$209.38	$209.40	$209.40
Purchase #6	$242.39	3.735%	$251.4433	$251.44	$251.45	$251.40
Purchase #7	$143.86	3.389%	$148.7354	$148.74	$148.75	$148.70
7 purchase totals =	$1,058.80		$1,127.9754	$1,127.98	$1,128.00	$1,127.90