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	$246.87	8.381%	$267.5602	$267.56	$267.55	$267.60
Purchase #2	$130.76	10.195%	$144.091	$144.09	$144.10	$144.10
Purchase #3	$207.44	8.802%	$225.6989	$225.70	$225.70	$225.70
Purchase #4	$55.59	6.460%	$59.1811	$59.18	$59.20	$59.20
Purchase #5	$11.60	8.579%	$12.5952	$12.60	$12.60	$12.60
Purchase #6	$211.27	7.790%	$227.7279	$227.73	$227.75	$227.70
Purchase #7	$157.38	3.326%	$162.6145	$162.61	$162.60	$162.60
7 purchase totals =	$1,020.91		$1,099.4688	$1,099.47	$1,099.50	$1,099.50