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	$133.86	6.799%	$142.9611	$142.96	$142.95	$143.00
Purchase #2	$147.70	4.866%	$154.8871	$154.89	$154.90	$154.90
Purchase #3	$48.95	13.332%	$55.476	$55.48	$55.50	$55.50
Purchase #4	$181.78	5.160%	$191.1598	$191.16	$191.15	$191.20
Purchase #5	$42.68	13.558%	$48.4666	$48.47	$48.45	$48.50
Purchase #6	$208.41	6.478%	$221.9108	$221.91	$221.90	$221.90
Purchase #7	$230.57	6.606%	$245.8015	$245.80	$245.80	$245.80
7 purchase totals =	$993.95		$1,060.6629	$1,060.67	$1,060.65	$1,060.80