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	$180.98	7.202%	$194.0142	$194.01	$194.00	$194.00
Purchase #2	$154.44	11.634%	$172.4075	$172.41	$172.40	$172.40
Purchase #3	$234.78	8.838%	$255.5299	$255.53	$255.55	$255.50
Purchase #4	$80.30	3.130%	$82.8134	$82.81	$82.80	$82.80
Purchase #5	$171.42	11.865%	$191.759	$191.76	$191.75	$191.80
Purchase #6	$128.61	11.280%	$143.1172	$143.12	$143.10	$143.10
Purchase #7	$192.35	3.558%	$199.1938	$199.19	$199.20	$199.20
7 purchase totals =	$1,142.88		$1,238.8350	$1,238.83	$1,238.80	$1,238.80