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	$156.78	3.333%	$162.0055	$162.01	$162.00	$162.00
Purchase #2	$128.28	13.278%	$145.313	$145.31	$145.30	$145.30
Purchase #3	$154.70	12.729%	$174.3918	$174.39	$174.40	$174.40
Purchase #4	$156.82	11.317%	$174.5673	$174.57	$174.55	$174.60
Purchase #5	$245.27	4.384%	$256.0226	$256.02	$256.00	$256.00
Purchase #6	$80.75	7.388%	$86.7158	$86.72	$86.70	$86.70
Purchase #7	$51.71	5.654%	$54.6337	$54.63	$54.65	$54.60
7 purchase totals =	$974.31		$1,053.6497	$1,053.65	$1,053.60	$1,053.60