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	$141.44	10.587%	$156.4143	$156.41	$156.40	$156.40
Purchase #2	$110.48	12.654%	$124.4601	$124.46	$124.45	$124.50
Purchase #3	$222.72	8.822%	$242.3684	$242.37	$242.35	$242.40
Purchase #4	$14.83	6.662%	$15.818	$15.82	$15.80	$15.80
Purchase #5	$223.92	11.869%	$250.4971	$250.50	$250.50	$250.50
Purchase #6	$81.28	3.249%	$83.9208	$83.92	$83.90	$83.90
Purchase #7	$191.84	10.245%	$211.494	$211.49	$211.50	$211.50
7 purchase totals =	$986.51		$1,084.9727	$1,084.97	$1,084.90	$1,085.00