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	$242.72	7.368%	$260.6036	$260.60	$260.60	$260.60
Purchase #2	$100.75	7.519%	$108.3254	$108.33	$108.35	$108.30
Purchase #3	$80.73	4.450%	$84.3225	$84.32	$84.30	$84.30
Purchase #4	$18.67	9.809%	$20.5013	$20.50	$20.50	$20.50
Purchase #5	$245.71	6.830%	$262.492	$262.49	$262.50	$262.50
Purchase #6	$167.27	12.117%	$187.5381	$187.54	$187.55	$187.50
Purchase #7	$134.99	12.471%	$151.8246	$151.82	$151.80	$151.80
7 purchase totals =	$990.84		$1,075.6075	$1,075.60	$1,075.60	$1,075.50