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	$222.64	11.396%	$248.0121	$248.01	$248.00	$248.00
Purchase #2	$142.91	12.264%	$160.4365	$160.44	$160.45	$160.40
Purchase #3	$66.55	4.138%	$69.3038	$69.30	$69.30	$69.30
Purchase #4	$98.95	5.114%	$104.0103	$104.01	$104.00	$104.00
Purchase #5	$167.38	6.645%	$178.5024	$178.50	$178.50	$178.50
Purchase #6	$133.31	8.654%	$144.8466	$144.85	$144.85	$144.80
Purchase #7	$185.66	6.801%	$198.2867	$198.29	$198.30	$198.30
7 purchase totals =	$1,017.40		$1,103.3984	$1,103.40	$1,103.40	$1,103.30