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	$112.72	3.156%	$116.2774	$116.28	$116.30	$116.30
Purchase #2	$190.76	4.334%	$199.0275	$199.03	$199.05	$199.00
Purchase #3	$167.86	5.634%	$177.3172	$177.32	$177.30	$177.30
Purchase #4	$236.85	13.106%	$267.8916	$267.89	$267.90	$267.90
Purchase #5	$91.44	9.755%	$100.36	$100.36	$100.35	$100.40
Purchase #6	$90.38	12.235%	$101.438	$101.44	$101.45	$101.40
Purchase #7	$120.45	11.705%	$134.5487	$134.55	$134.55	$134.50
7 purchase totals =	$1,010.46		$1,096.8604	$1,096.87	$1,096.90	$1,096.80