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	$207.42	3.854%	$215.414	$215.41	$215.40	$215.40
Purchase #2	$225.67	13.648%	$256.4694	$256.47	$256.45	$256.50
Purchase #3	$98.31	10.446%	$108.5795	$108.58	$108.60	$108.60
Purchase #4	$179.89	6.335%	$191.286	$191.29	$191.30	$191.30
Purchase #5	$240.33	3.633%	$249.0612	$249.06	$249.05	$249.10
Purchase #6	$170.40	8.618%	$185.0851	$185.09	$185.10	$185.10
Purchase #7	$150.56	3.663%	$156.075	$156.08	$156.10	$156.10
7 purchase totals =	$1,272.58		$1,361.9702	$1,361.98	$1,362.00	$1,362.10