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	$182.49	12.597%	$205.4783	$205.48	$205.50	$205.50
Purchase #2	$250.61	12.590%	$282.1618	$282.16	$282.15	$282.20
Purchase #3	$119.82	13.784%	$136.336	$136.34	$136.35	$136.30
Purchase #4	$25.60	11.349%	$28.5053	$28.51	$28.50	$28.50
Purchase #5	$203.64	12.818%	$229.7426	$229.74	$229.75	$229.70
Purchase #6	$49.90	11.469%	$55.623	$55.62	$55.60	$55.60
Purchase #7	$172.36	10.551%	$190.5457	$190.55	$190.55	$190.50
7 purchase totals =	$1,004.42		$1,128.3927	$1,128.40	$1,128.40	$1,128.30