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	$22.39	5.686%	$23.6631	$23.66	$23.65	$23.70
Purchase #2	$239.90	6.220%	$254.8218	$254.82	$254.80	$254.80
Purchase #3	$174.65	12.618%	$196.6873	$196.69	$196.70	$196.70
Purchase #4	$159.30	5.233%	$167.6362	$167.64	$167.65	$167.60
Purchase #5	$178.76	10.116%	$196.8434	$196.84	$196.85	$196.80
Purchase #6	$104.34	4.834%	$109.3838	$109.38	$109.40	$109.40
Purchase #7	$140.80	7.593%	$151.4909	$151.49	$151.50	$151.50
7 purchase totals =	$1,020.14		$1,100.5265	$1,100.52	$1,100.55	$1,100.50