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	$95.91	7.458%	$103.063	$103.06	$103.05	$103.10
Purchase #2	$243.81	12.847%	$275.1323	$275.13	$275.15	$275.10
Purchase #3	$120.50	10.172%	$132.7573	$132.76	$132.75	$132.80
Purchase #4	$236.61	11.473%	$263.7563	$263.76	$263.75	$263.80
Purchase #5	$25.51	11.392%	$28.4161	$28.42	$28.40	$28.40
Purchase #6	$151.81	3.265%	$156.7666	$156.77	$156.75	$156.80
Purchase #7	$223.70	6.681%	$238.6454	$238.65	$238.65	$238.60
7 purchase totals =	$1,097.85		$1,198.5370	$1,198.55	$1,198.50	$1,198.60