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	$86.31	13.705%	$98.1388	$98.14	$98.15	$98.10
Purchase #2	$202.59	8.451%	$219.7109	$219.71	$219.70	$219.70
Purchase #3	$213.77	6.453%	$227.5646	$227.56	$227.55	$227.60
Purchase #4	$121.91	7.833%	$131.4592	$131.46	$131.45	$131.50
Purchase #5	$108.72	9.315%	$118.8473	$118.85	$118.85	$118.80
Purchase #6	$60.34	4.299%	$62.934	$62.93	$62.95	$62.90
Purchase #7	$206.30	7.323%	$221.4073	$221.41	$221.40	$221.40
7 purchase totals =	$999.94		$1,080.0621	$1,080.06	$1,080.05	$1,080.00