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	$187.77	6.380%	$199.7497	$199.75	$199.75	$199.70
Purchase #2	$40.77	4.593%	$42.6426	$42.64	$42.65	$42.60
Purchase #3	$237.58	12.787%	$267.9594	$267.96	$267.95	$268.00
Purchase #4	$25.60	7.470%	$27.5123	$27.51	$27.50	$27.50
Purchase #5	$198.72	8.444%	$215.4999	$215.50	$215.50	$215.50
Purchase #6	$229.39	10.564%	$253.6228	$253.62	$253.60	$253.60
Purchase #7	$164.33	8.525%	$178.3391	$178.34	$178.35	$178.30
7 purchase totals =	$1,084.16		$1,185.3258	$1,185.32	$1,185.30	$1,185.20