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	$206.84	7.380%	$222.1048	$222.10	$222.10	$222.10
Purchase #2	$82.74	7.751%	$89.1532	$89.15	$89.15	$89.20
Purchase #3	$98.72	4.604%	$103.2651	$103.27	$103.25	$103.30
Purchase #4	$63.38	10.628%	$70.116	$70.12	$70.10	$70.10
Purchase #5	$213.81	5.315%	$225.174	$225.17	$225.15	$225.20
Purchase #6	$210.59	8.259%	$227.9826	$227.98	$228.00	$228.00
Purchase #7	$111.63	3.444%	$115.4745	$115.47	$115.45	$115.50
7 purchase totals =	$987.71		$1,053.2702	$1,053.26	$1,053.20	$1,053.40