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	$140.72	9.865%	$154.602	$154.60	$154.60	$154.60
Purchase #2	$179.98	3.693%	$186.6267	$186.63	$186.65	$186.60
Purchase #3	$129.92	8.862%	$141.4335	$141.43	$141.45	$141.40
Purchase #4	$98.53	6.801%	$105.231	$105.23	$105.25	$105.20
Purchase #5	$173.57	10.564%	$191.9059	$191.91	$191.90	$191.90
Purchase #6	$134.65	4.379%	$140.5463	$140.55	$140.55	$140.50
Purchase #7	$119.59	9.338%	$130.7573	$130.76	$130.75	$130.80
7 purchase totals =	$976.96		$1,051.1027	$1,051.11	$1,051.15	$1,051.00