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	$98.60	5.462%	$103.9855	$103.99	$104.00	$104.00
Purchase #2	$145.46	7.428%	$156.2648	$156.26	$156.25	$156.30
Purchase #3	$24.56	5.473%	$25.9042	$25.90	$25.90	$25.90
Purchase #4	$133.41	10.381%	$147.2593	$147.26	$147.25	$147.30
Purchase #5	$75.54	3.468%	$78.1597	$78.16	$78.15	$78.20
Purchase #6	$134.31	3.666%	$139.2338	$139.23	$139.25	$139.20
Purchase #7	$176.43	12.566%	$198.6002	$198.60	$198.60	$198.60
7 purchase totals =	$788.31		$849.4075	$849.40	$849.40	$849.50